Learning electronics: Release the Magic Blue Smoke

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Delta-Wye: Sep 29, 2005

I was reading this site: http://users.pandora.be/worldstandards/electricity.htm and it has the following information on it:

quote:

Europe and most other countries in the world use a voltage which is twice that of the US. It is between 220 and 240 volts, whereas in Japan and in most of the Americas the voltage is between 100 and 127 volts.

The system of three-phase alternating current electrical generation and distribution was invented by a nineteenth century creative genius named Nicola Tesla. He made many careful calculations and measurements and found out that 60 Hz (Hertz, cycles per second) was the best frequency for alternating current (AC) power generating. He preferred 240 volts, which put him at odds with Thomas Edison, whose direct current (DC) systems were 110 volts. Perhaps Edison had a useful point in the safety factor of the lower voltage, but DC couldn't provide the power to a distance that AC could.

When the German company AEG built the first European generating facility, its engineers decided to fix the frequency at 50 Hz, because the number 60 didn't fit the metric standard unit sequence (1,2,5). At that time, AEG had a virtual monopoly and their standard spread to the rest of the continent. In Britain, differing frequencies proliferated, and only after World War II the 50-cycle standard was established. A mistake, however.

Not only is 50 Hz 20% less effective in generation, it is 10-15% less efficient in transmission, it requires up to 30% larger windings and magnetic core materials in transformer construction. Electric motors are much less efficient at the lower frequency, and must also be made more robust to handle the electrical losses and the extra heat generated. Today, only a handful of countries (Antigua, Guyana, Peru, the Philippines, South Korea and the Leeward Islands) follow Tesla�s advice and use the 60 Hz frequency together with a voltage of 220-240 V.

Originally Europe was 120 V too, just like Japan and the US today. It has been deemed necessary to increase voltage to get more power with less losses and voltage drop from the same copper wire diameter. At the time the US also wanted to change but because of the cost involved to replace all electric appliances, they decided not to. At the time (50s-60s) the average US household already had a fridge, a washing-machine, etc., but not in Europe.

The end result is that now, the US seems not to have evolved from the 50s and 60s, and still copes with problems as light bulbs that burn out rather quickly when they are close to the transformer (too high a voltage), or just the other way round: not enough voltage at the end of the line (105 to 127 volt spread !).

Note that currently all new American buildings get in fact 240 volts split in two 120 between neutral and hot wire. Major appliances, such as virtually all drying machines and ovens, are now connected to 240 volts. Mind, Americans who have European equipment shouldn't connect it to these outlets. Although it may work on some appliances, it will definitely not be the case for all of your equipment. The reason for this is that in the US 240 V is two-phase, whereas in Europe it is single phase.

If you look at the map they include, a large portion (and notably, China and India) are at 50 Hz. Do they actually mean 20% less than 60 Hz? It seems like 20% of Europe and Asia is a shitload of energy, and a gigantic waste of that energy to boot. I can believe it's less efficient, but I have a hard time buying these numbers - they just don't pass my bs filter. What do you guys think?

# ¿ Jan 26, 2008 21:13

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# ¿ May 4, 2024 04:52

Delta-Wye: Sep 29, 2005

babyeatingpsychopath posted:

I'm asking because it doesn't make sense (to me) to have a resistor when using a single AA battery to light an LED with a max drop of 1.4V. If the battery starts at 1.4V max and only gets lower as it discharges, why put more components in the circuit?

Here is an example IV curve I ripped out of a random Vishay datasheet:

The big issue here is to recognize how steep the IV curve is - a change of less than .1 V can double your current (or half it). Variations in both the LED and the battery will make it impossible/near impossible to get a constant brightness out of the LED. Alkaline batteries (1.5Vish) are especially bad at this as the voltage drops a significant (in this application) amount over the life of the battery. The life of the LED is could be a concern too if your circuit overdrives it.

If you wanted a simple supply->led circuit, a current supply would make much more sense as you could bias the LED at exactly the brightness you want, but I suspect building a current supply vs. adding a resistor doesn't save you components.

Delta-Wye fucked around with this message at 21:48 on Feb 7, 2008

# ¿ Feb 7, 2008 19:38

Delta-Wye: Sep 29, 2005

Comrade Milton posted:

Sorry to bother everyone, but I have a question I need answered urgently to complete a project for a friend.

I have 2 red LEDs 5mm 18volt 20mA 120mcd and 2 3volt CR2025 Lithium disc batteries and I need to know what resistor is needed between each LED and battery (they'll be completely separate circuits).

Please PM, e-mail nthoms@gmail.com or reply to thread. Sorry to bust in with this trivial request; I had notations for the proper parts, but I don't know where they are and I don't have time to begin reading all of the posted texts to try to sift through just for this answer.

The sifting can begin once I've calmed and made the proper circuits so I don't burn out my pretty LEDs.

Thanks!

Sorry to say, but it's impossible to directly power 18V LEDs with 3V batteries.

EDIT:

quote:

I didn't know how to calculate the solution.

Can you not subtract and divide? (Vbatt - Vforward) / I = R. Ohm's law yo. Don't act like a retard and people won't treat you like one.

Of course, given your information, I get (3 - 18) / 20mA = -750 ohms. Good luck finding that component!

Delta-Wye fucked around with this message at 19:24 on Mar 18, 2008

# ¿ Mar 18, 2008 19:17

Delta-Wye: Sep 29, 2005

Jdohyeah posted:

Don't be so condescending man, he made a typo. Your reds, ambers and yellows are generally 1.8 - 2.4V, it's pretty obvious what he meant

It's not the typo - it's the fact he's DEMANDED we help him (and HOW DARE WE QUESTION IT) and he can't even be bothered to copy down the values correctly.

# ¿ Mar 19, 2008 04:03

Delta-Wye: Sep 29, 2005

Delivery McGee posted:

Some of them mention in passing that "you could just connect it to the volume pot," but my volume pot has a lot of pins and no labels, so I don't know what would go where.

How many is a lot? Its probably still your best bet, so you should consider using continuity on your multimeter to see if you can work out where they go (if its a combined power switch, for instance, I suspect one goes to the 12V bus on your car, one to the 12V bus on the unit, etc). If you can narrow it down to a few pins (2 or 3) I think it could be figured out.

# ¿ Mar 19, 2008 21:44

Delta-Wye: Sep 29, 2005

Delivery McGee posted:

Looking at the little wheels turning through the slots in the body, it appears that there are eight on the volume part (in two sets of four), two on the power-switch part, and six (in two sets of three) on the other part that I forget what it does.

It has (apparently) four pins per channel. What's the other one? Just separate grounds for input/output?

Edit: poked at it with the meter. First pin is ground, second pin is the output to amp, third pin is open, fourth pin is the input. Now what do I do with them?

Should be able to solder leads to the input ones and see what happens. Can't imagine it would hurt anything to try, at any rate. Might want to clip/unsolder the connection eventually so that your radio doesn't get mixed in. You could mount a switch (which would be pimp) to select between radio and aux.

Was thinking about this today - would it be appropriate to include bypass capacitors to prevent any DC bias thats present from affecting whatever he's plugging in? This is the sorta thing I'd experiment with (I missed taking EE 272 - Hacking consumer electronics :v:

) and just see if it works.

quote:

I didn't demand, I asked. My typo was a period. In short: get hosed.

Let me be more specific. You didn't come into this thread saying "hey guys, I'm unclear about X, could you explain it?" but instead you came in saying "hey, I need to do this thing but I'm too lazy to type in 'LED resistor current calculator' into Google (btw, the whole first page is pretty relevant) and read. I found this thread, but am again too lazy to read. Please do the work for me, because I am too lazy, document it, and email it to me where it will do no one else any good. kthxbye". It would have taken you LESS time to do a google search then type up your post asking for the result to be given to you. The fact that there is an obvious typo, plus the rest of the post, made the whole thing reek of self-centered absorption.

You didn't miss a period, by the way, you missed a decimal point, which had a significant change to the values you had given. While it is pedagogical for me to not simply put it back in, these kind of mistakes are pretty obvious and should have been caught with a little bit of proofreading (but I guess you were too lazy...)

I gave you the answer you required, as you asked, I just gave you some poo poo along with it. If you really want to tell me to 'get hosed' cause I wasn't nice about doing your work, go right ahead, but it certainly doesn't make me feel BAD about giving you poo poo - quite the opposite really.

Delta-Wye fucked around with this message at 10:21 on Mar 20, 2008

# ¿ Mar 20, 2008 10:08

Delta-Wye: Sep 29, 2005

Cuw posted:

wouldn't you need a TPDT swtich for that? You have 3 channels that need switching, left, right, ground(Well ground might not need switching but left and right do). I would think a simple slide switch would work pretty well and would only cost a dollar or two at mouser.

A DPDT switch would be required I think. The Am/FM switch hole may give him room to mount the replacement switch though.

# ¿ Mar 20, 2008 18:29

Delta-Wye: Sep 29, 2005

jovial_cynic posted:

I understand how the resistors relate to the gain on an op-amp circuit now. In terms of strictly amplifying the signal coming from an instrument pickup, is an increase in gain the minimum requirement to get the sound from the instrument to make something happen in the speakers?

For instance, I've got this simple circuit diagram based on an op-amp:

The chip datasheet states that it can be powered with voltages as low as 6v, so I imagine I can run this off of a 9v battery.

Is this circuit all that's necessary to make a mini guitar amp? I've seen op-amps used as the basis for a pre-amp, but I've never seen a simple op-amp based guitar amp, so I'm not sure.

Am I missing something?

There is the issue of impedance matching, which an op amp assists with because it has a large input resistance and a low output resistance (http://www.tape.com/resource/impedance.html is the first result I found that explains what I mean).

Notice that the opamp uses a bipolar supply (+V and -V). If it takes voltages as low as +/- 6V, then you will not be able to power it with a 9V battery without some sort of charge pump. If it takes voltages as low as +/- 3V (not sure exactly what you meant by "low as 6v") you can power it from a 9V batter with a voltage divider (kinda ghetto, but the accepted solution for this task). The problem with a resistive voltage divider is that any change to the load affects the output voltage, and this effect is magnified as the resistance goes up (voltage accuracy is inversely porportional to power efficiency). For a battery powered device, this can be a big concern.

A simple circuit like this would make a fine headphone amp, I think (haven't read the 4558 datasheets yet, but it should be fine). The big issue for a headphone amp is a bit of gain, coloring for the signal, and impedance matching, and I think that circuit can be made to do all of those things. Not sure if the gain is enough to create clipping, but another stage could be added to add distortion if it doesn't, for instance, but it would give at least good performance clean.

However, I have some reservations if it would make a good guitar amp - it certainly isn't going to be driving a 4x12" marshall cab or anything anytime soon.

# ¿ Mar 20, 2008 19:28

Delta-Wye: Sep 29, 2005

Comrade Milton posted:

I didn't even know how to phrase what I didn't know, so Google wasn't of much use.

You realize the two are the same thing, right? Small, identical dots? Just that one comes with grammar and the other with numeric values? I don't know if they teach anything except equations and being a smug prick at engineering school.

I actually had two semesters on how to be a smug prick at engineering school. Kinda on topic, check out my new shirt I got today.

I won't deny that we/me can be dicks sometimes.

Plus, if you can't type "led battery resistor" (key words from your post) into google and read the first result, you are more retarded then I previously expected.

quote:

Regarding the v6 source, you guys are speaking a little over my head. All I know is that by looking at this page, it says "Supply Min = 6 Volt; Supply Max = 36 Volt". And when I look at the LM386 cover sheet, it says that the chip has a "Wide Supply voltage range: 4V-12V" And knowing that the LM386 can be powered by a 9v, I assume that the meaning is similar -- any DC power supply between 6v and 36v (like a 9v battery) will work for the KA4558.

Am I reading that incorrectly?

Those are the min/max values for the voltage inputs, most likely. You'll have to supply something in between to get the expected output. Here is a schematic showing what I mean:

If R1 and R2 are equal, the output values should be fairly close to the expected values until the loading circuit (your op amp business) is connected. Larger values of R1/R2 are more efficient, but if they are bigger than your loading circuit's equivalent resistance, the output voltages may not be very accurate (due to parallel resistances being significantly lower).

# ¿ Mar 21, 2008 04:23

Delta-Wye: Sep 29, 2005

Corla Plankun posted:

I actually built a really ghetto single op-amp amplifier for my guitar a couple weeks ago. I used a 9 volt AC adapter, and absolutely no fancy split-power supply. It sounds really distorted (and awesome, for my application: playing a super crappy squier into a pair of headphones) and I just assumed thats what Op-Amps did, and thats why they're 50 cents a piece at radio shack.

Are you guys suggesting that if I linked it to a split power supply, it would amplify without wonky low-fi distortion? I like it the way it is, but I'm also quite curious.

There could be a number of things up with your design. It could just be a lovely opamp (it WAS from radioshack, after all), it could be not having a bipolar supply, or it could be a lack of negative feedback. I would be interested in hearing if adding a bipolar supply would clean the signal up. Opamps are limited by their rail (supply) voltages - it can't output a higher level than you put in. If your supply is +9/0V, you will only amplify the positive portions of the signal at best. If you're lacking negative feedback, your gain is going to be ~10,000 and the opamp is just going to be swinging from one rail to the other (or from 0-9V in your case).

If adding a bipolar supply and having negative feedback cleans it up, and you want a dirty signal again, adding two diodes back to back across the feedback resistor should get you some clipping. Ought to be a bit better sounding than what you currently have, at any rate.

# ¿ Mar 21, 2008 10:34

Delta-Wye: Sep 29, 2005

mtwieg posted:

A resistor divider should work fine, as long as you account for it's impedance. It should be high enough that it won't load down the sensor, but low enough that the ADC sampling capacitor will charge fully in the sample period. Check the datasheet for the sensor and your adc. You'll likely find that there is a good range of impedance that will work. If the impedance is too much for your adc, you could slow down its sampling time, or buffer the signal with an op amp. If the op amp is good (something with low offset in the microvolt range), the error should be negligible.

Don't want to sound retarded, but if he's buffering with an opamp anyways, couldn't he dump the R-divider completely, and just use an opamp amp with a gain of 3.3/5 ~= .66?

EDIT: maybe this is what you mean *shrug*

# ¿ Apr 21, 2008 07:51

Delta-Wye: Sep 29, 2005

I'm thinking about building a metronome, and shopping for some components. Has anybody had any experience with little LCD character modules? (http://www.lumex.com/product.aspx?id=463) The datasheets are wonderfully vague. I was hoping to drive the characers with digital i/o ports like a 7 segment display (but using less power, hence LCD) but it claims it wants 5V AC. Does this have to be true AC? would rapidly switching DC be alright? does this mean 0-5V or -5-5V? So many unanswered questions, and I really don't feel like ordering one to blow up experimenting with/decide it won't meet my requirements.

# ¿ May 28, 2008 23:59

Delta-Wye: Sep 29, 2005

turbo sex bat 4000 posted:

IIRC you have to switch the 0/5V back and forth at a few hundred Hz so that it doesn't die. It doesn't need a sine wave, just alternating polarity.

That would be fairly trivial. When you say alternating polarity, does that mean the common leg should be 2.5V? If not, does this vary from PWM at all (which is what it sounds like)? Thanks!

# ¿ May 29, 2008 05:21

Delta-Wye: Sep 29, 2005

turbo sex bat 4000 posted:

It is different from PWM. You want to switch the common between 0 and 5V rapidly. To turn on a segment, you switch the desired pin out of phase with the common.
code:
--- = 5V
___ = 0V

Common              ___---___---___---

Segment a (visible) ---___---___---___

Segment b (Off)     ___---___---___---
Something like that

You should write datasheets or something buddy. That made a hell of a lot more sense than most anything I've been able to find on google. If you don't mind one more question, any ballpark idea on current draw? I assume by being out of phase with the common, you get a little current flow either way. Does it average close to zero or so? I ask as I'm trying to decide if I want to drive the digits directly, or through logic.

# ¿ May 29, 2008 05:52

Delta-Wye: Sep 29, 2005

ante posted:

You're supposed to say that you couldn't resist

or it was really conductive to learning.

# ¿ Jun 15, 2008 07:39

Delta-Wye: Sep 29, 2005

Jonny 290 posted:

I slaved all weekend on a bipolar linear supply and a TL082 preamp because I was sick of rigging up divider networks, and assumed that 78xx and 79xx regulators had the same pinout. WRONG-O.

I too learned this one day, the same way. One of my grad student buddies told me its so you can mount them back to back on a heatsink or something. (EDIT: He's a liar. My whole life is a lie. See below. It doesn't make a lick of sense according to the datasheet) For whatever reason, it pissed me right the gently caress off.

Delta-Wye fucked around with this message at 09:15 on Jun 16, 2008

# ¿ Jun 15, 2008 20:37

Delta-Wye: Sep 29, 2005

Behold! For I have ridden the mighty moon worm!

Actually, not really, but I DID upload my mypic32 project proposal, the Automated Go Board. I would appreciate it if you fine folks would check it out and give me some feedback!

# ¿ Jun 27, 2008 09:15

Delta-Wye: Sep 29, 2005

Mr. Powers posted:

I think you're going to get whacked for efficiency. The 10 16F slave PICs are mostly going to be unused. I think you'd be better off looking at various serial peripherals you can use. I know for a home project of mine, I plan to use an SPI-based LED driver. You could cascade as many of these as you want, to control a ton of LEDs, or you could just have a few and multiplex the board's display. You could probably get away with very basic resistive touch joints for each position on the board using a FET to turn it into an appropriate digital signal which you could then multiplex or use shift registers. It might be easier than dealing with analog multiplexing and capacitive touch buttons.

Probably, but keep in mind that this is put on by microchip - the PICs, PIC32, and mTouch crap is there to make them feel relevant and loved

# ¿ Jun 27, 2008 17:48

Delta-Wye: Sep 29, 2005

Sound_man posted:

I have a little project in mind to make me the smart intern at work and I would like to double check it here before I send it to my boss. Part of my daily task is checking 19 pin connectors that each contain 6 circuits to make sure each circuit is getting around 208 volts AC. The way they have me doing it now is with a multi meter which doesn't take too terrible long but still a pain in the rear end compared to something like a 19 pin plug with a bunch of neons on it. I was looking at parts and it seems that something like this http://www.cml-it.com/pdf/4-17.pdf model # 2151A1 would be perfect for the job. Wire it up between the two hot phases and its good to go right? My concern is that depending who else is using juice the output can drop to something closer to 205 volts AC which is ok for what we are doing but what is the tolerance for neons? they would still light up, perhaps just dimmer correct? This just seems to be too simple to work and not have been done by someone else in my position.

Sounds like a plan if your only failure mode is complete failure. I'm not sure if you need a series current limiting resistor - I've seen NE-2 bulbs with them, but I don't know if it's required or was simply a brightness calibration thing.

Delta-Wye fucked around with this message at 19:31 on Jul 11, 2008

# ¿ Jul 11, 2008 19:29

Delta-Wye: Sep 29, 2005

Metajo Cum Dumpster posted:

Read and skimmed through all of this thread and didn't see exactly this question answered so here goes;

I'm completely new and currently really stupid when it comes to electronics, but very interested in learning. I'm wondering what I need to buy as the "essentials" for starting on a breadboard;

So far I'm ordering
-"Getting Started in Electronics"
-"There are no Electrons"
-Multimeter
-Breadboard (800+ holes?)
-300+ pc wire kit

What else do I need to start off with to do the simple circuits in those books and elsewhere?

What grab bags should I get from Jameco for which components? What kind of power source, wall wart? What kind to go with the breadboard? Are the prepackaged $10 kits you can get everywhere a good learning tool outside of soldering?

Thanks! This has been a fun thread to read (the 25% of it I could actually understand).

What kind of stuff are you planning on getting involved with? If you're doing analog stuff (guitar pedals or something, I don't know) versus microcontroller stuff, the amount and kind of components you'll need is pretty different. When I started my collection of parts, I started with a Schwab's kit, which gave me a bit of everything, which is nice. But when you're designing something, and you want a certain resistor, its a pain in the rear end to search through a couple hundred mixed resistors to find the value you want (although its good practice to learn the color codes). I ended up with the following kits:
Resistor selection
Ceramic cap selection

It's a bit of an investment at the beginning, but oh boy does it make prototyping so much more enjoyable. Another nice thing with those kits is they have extra drawers/labels for other stuff you might end up with (transistors or whatever). I also bought a wiring kit which made breadboarding much more pleasant. If you don't get the kit, a few feet of ethernet is a great source for jumper wires. I'd get a grab bag of electrolytics (they're pretty easy to find what you're looking for 'cause the labeling is fairly clear, and I mostly use them for power supply filtering or whatever where particular values aren't real critical).
As far as power supplies go, a wallwart + 78XX wouldn't be a bad idea, but I think building your own would be a great first project. Get a project box, transformer, the correct 78XX/79XX you're interested in, AC receptacle, diodes, filter cap, output jacks (banana plugs?) and you're all set. It sounds like a lot, but the circuit is pretty straightforward (if you can't find anything online, I/we could easily help you design it in this thread). You can even get fancy and put in a LM317 for a variable output, whatever does it for you.

Some other parts you should buy (things I use/see used a lot):
555/556 Timing ICs
Logic ICs (some NAND gates, a few hex inverters, maybe some others go crazy here)
OP Amps (at least a few 741s if nothing else)
Discrete semiconductors (1n4148 1n914 1n4001 diodes, 2n2222 NPN transistors, 2n3904/2n3906 NPN/PNP transistors, 2n7000 mosfets)
Regulator ICs (7809/7805/lm317, etc)
If you're interested in microcontrollers, a programmer and some ones to start with would be handy (such as a Pickit2 or something)

dv6speed posted:

I order just about all my electronics parts from http://mouser.com

They don't have a minimum order, are quite friendly, and very fast.

I usually order from mouser as well - they have an awesome selection, and great prices especially on bulk (100s of diodes or whatever) or usually pretty fair. However, their great selection is a bit overwealming for a beginner, it was for me at least. How the hell is someone supposed to know if they need a ne555p or ne555agpr (there are ~133 555 varients on mouser). Sometimes it's obvious based on package or whatever, sometimes it's not. Jameco has some nice kits and a smaller selection (something like 4 555s to wade through, for example) that would be sufficient for someone starting out. Just my two cents and all, but I rate the big suppliers as:
Digikey -> Mouser -> Jameco, in my experience, going from biggest/most annoying selection to smallest/easiest selection. I started at Jameco and now order mostly from Mouser. *shrug* I also order oddball stuff from Sparkfun Electronics a lot. They specialize in microcontrollers and exotic sensors. If you're doing guitar electronics, Small Bear Electronics is hard to beat. Ebay, believe it or not, has been a good place for LEDs in my experience, although they've always shipped from Hong Kong which takes a while.

EDIT: Goddamn, thats some :words:

. If you'd list of a few projects/areas you're interested in, you'd probably get more specific replies.

# ¿ Jul 18, 2008 20:30

Delta-Wye: Sep 29, 2005

Metajo Cum Dumpster posted:

1/2 1/4 1/8 watt carbon filter resistors?

That is the power rating - watts is current x voltage. For most stuff (especially digital electronics) 1/8W is both the standard and perfectly acceptable. There are some situations where you might need a higher power resistor, but in my experience its been pretty rare - and when I do I sometimes just fake it with an array of lower power resistors.

Metajo Cum Dumpster posted:

Radial, disc, axial ceramic resistors?

Formfactor, mostly. Radial, disc, and axial refer to where the leads come out. Are you sure you didn't mean capacitors here?

Metajo Cum Dumpster posted:

There's about 1000 other categories for each component, does it matter much now to know specifically the voltage, tolerance, temp coefficient, size, pitch, termination, etc? I warned you I know jack poo poo about all this.

Sometimes yes, sometimes no. For instance, the voltage rating on an electrolytic cap is extremely important - go outside of it and its liable to go pop (and out goes the magic blue smoke!). However, long as it's greater than the voltage the cap will be subjected to, it hardly matters what it actually is rated for (aka, if you are filtering 12V DC and use a cap rated for 300V, it will be perfectly fine if a bit of an overkill). Other stuff like temp coefficient doesn't really matter much unless you are engineering a device where you will be subjecting it to a wide range of temps (or selling a million units all over the country or whatever) and you have to know what range the resistance (or other pertinant value) shifts over the possible temps the device will be exposed to. On your workbench inside a normal house, it doesn't matter at all.

Metajo Cum Dumpster posted:

To Delta-Wye's question, I'm not interested in the analog musical stuff. I'm definitely interested in working with the ICs/etc. I want to make a 2-digit up down counter at some time with a reset and preset numbers.

And this is why I asked it

Make sure you order a ton of counter ICs (although that should be obvious to you). I would consider getting some of the other ICs for shits and giggles - a 741 can be used to generate a square wave input from some sort of analog sensor system, for example, or a 555 can be used to automatically increment your counter circuit for testing. Just curious, what purpose will this counter circuit serve? I recently got a load of counters to try and build a logic-based nixie clock, and it's a neat approach to the problem (as opposed to my normal 'stuff a pic in it' solution).

# ¿ Jul 18, 2008 21:59

Delta-Wye: Sep 29, 2005

Metajo Cum Dumpster posted:

They don't have IC grab bags do they?

For kits:
74LS SERIES
CD4000 SERIES
LINEAR SERIES
7400 SERIES
Kinda spendy. Jameco also has assorted IC grab bags, but I've heard the selection is sometimes lovely (might have even been earlier in this thread, someone had something like 33% lovely motorola sound chips or something). I'd almost recommend ordering those seperately - save money, and keep your selection smaller. I know I wouldn't know what the hell to do with a 74ls171 or whatever without reading the datasheet, and without reading a 100 datasheets, I'd have no idea what I had on hand so I wouldn't know what where to start. It's up to you and your budget though, different strokes, all that.

Metajo Cum Dumpster posted:

I just wanted to make the counter as a way to counting the number of times I open certain thigs. IE my refrigerator (not a fatty), my apartment door, etc. And I just wanted the countdown part of it with a settable number because...I...reallydon't know, I just want to make it.

Don't let me discourage you at all, sounds entertaining. You're not the first person to make a silly counter gadget, and these guys are "professionals".

# ¿ Jul 18, 2008 22:29

Delta-Wye: Sep 29, 2005

I rarely finish projects, I'm easily distracted. However, I recently finished a pedal supply so I could save on batteries and unplugging/plugging my pedals.

Still need to decal/paint it, but thats secondary I suppose. It's a pretty straightforward transformer->rectifier->filter->regulator circuit. Went a little crazy adding caps to the outputs

Probably wouldn't hurt to isolate the outputs better, but I don't notice any additional noise or hum doing this as opposed to batteries. Have two more project boxes/switches so now I need to find a few more pedal projects to do. Before that, I think I need to revamp some of my bench equipment. I have a function generator breadboarded and am doing the layout currently.

I've also been thinking about redsigning my sad little bench DC power supply. It works at outputting voltage alright I guess, but it's not very smart. There is no feedback and no current limiting. I was thinking something like this would be a good project. The switching backend keeps the voltage drop across the linear supply reasonably low, and the linear supply gets rid (hopefully) of most of the switching noise. I think I can replace the control pot with a digital pot so it can be controlled by a microcontroller, which would be cool. I'm currently working on prototyping the linear section as drawn and a current controlling section that I penciled out and think will work. My overarching plan is to control the current limit and voltage limit via a microcontroller.

quote:

I've got a small heap of IRF 3415 mosfets lying around (150V 43A abs max) These are N-channel, and I'd like some P-channel with similar capabilities for building H-bridges and the like. Any suggestions? I've had a hard time finding anything similar. (I don't necessarily need a particular transistor, just places/ways to find them)

Poking around on mouser, the FQA36P15 is a 150V/36A P-Channel MOSFET. I found it by simply going to their MOSFET page and choosing p-channel and high voltage and current requirements, and reading through the 30 or so it returned. One thing I've always hated about electronics is the naming conventions - without a lot of experience, how the hell is someone supposed to tell which semiconductors should be used where?

I have a drawer for 2N2222s, 2N3904s, MPSA42s, BC237Bs, BC547Bs, 2N5088s, 2N5089s, and 2N4401 NPN transistors (and thats just the sorted NPNs!). Some of them have obvious features that differentiate them (the MPSA42 is for high-voltage work, for example) but for the most part I wouldn't know whether to use a 2N5088 or 2N5089 unless either someone told me or I compare/contrast datasheets for hours

Does anyone have any naming convention guides or explanations? About all I know is the 2N, 1N business refers to the number of junctions in the device. Other than that, the most basic of details, :iiam:

Delta-Wye fucked around with this message at 09:33 on Jul 25, 2008

# ¿ Jul 25, 2008 08:39

Delta-Wye: Sep 29, 2005

thepartypooper posted:

I want to pick up a 2-line alphanumeric LCD to work with, since I've never touched them before. However, data sheets for these seem to be universally sparse; usually little more than a mechanical drawing.

I've come across a few that say they are Hitachi HD44780 compatible, so I've picked up that datasheet. Is this the case for most parallel LCD's? If the datasheet doesn't say otherwise, should I assume that this is the interface?

I think assuming it's HD44780 compatible is a good guess - that chipset is so ubiquitous even it it was some other chip, it probably uses the same command format. Sparkfun sells a serial backpack for the parallel interface LCDs - while you may not want to buy it (I wouldn't) they link to the source code and schematics because they're cool like that. They might be of assistance if you get stuck and reverse engineering their information is easier than moving forward.

Delta-Wye fucked around with this message at 00:36 on Jul 26, 2008

# ¿ Jul 25, 2008 20:44

Delta-Wye: Sep 29, 2005

Astrolite posted:

Thanks! I found them on ebay for $2.13 a pop. Think I'll just have to give them a try. The same seller has some insane transistors though. 1200V 54A? I had no idea you could do something like that in a TO247 package.

I would suspect that the power rating is sane - aka the transistor works best either fully on or fully offbut will explode with 1200V across and 54A through it (that's loving 65kW goddamn).

# ¿ Jul 26, 2008 00:36

Delta-Wye: Sep 29, 2005

Keebler posted:

Thanks, it's looking like I have to go to the TSOP package anyway. It doesn't look like they sell through hole SOJ sockets. I'll have to pickup a few cheap parts to practice on. Poking around I see people even do it using a toaster over! Maybe I'll give that a shot for shits and giggles.

Skillets look better than toasters for smd work.

# ¿ Aug 13, 2008 18:52

Delta-Wye: Sep 29, 2005

I want to try and make a metronome, and I'm at a bit of a loss with how to create the clicks. I'd like to get the output from a microcontroller to make the clicking sound, and mix it with an already present audio signal. A simple 2channel active mixer would be simple to design, but I'm not sure how to make the clicks. I suspect a simple high-low transition would result in an audible click, but would it be nicer sounding to do several transitions (say, at 440 Hz or whatever) for a very short amount of time to get more of a beep? Do you guys think that a short beep-styled signal would stand out and sound good?

# ¿ Nov 6, 2008 20:50

Delta-Wye: Sep 29, 2005

mtwieg posted:

well I suppose a click is just a pulse, and doing many pulses would give you a tone. Or perhaps you do want a tone, but you want its amplitude to diminish quickly. I'm not really sure what a click looks like as a signal. Maybe try recording some and looking at the wave forms in an oscilloscope. In any case a simple digital output may not be able to yield what you want, unless you do a digital to analog conversion via PWM or something.

I only have my analog scope handy, which is great for periodic signals but looking at a single click would be a bit hard. I might just have to experiment a bit and see what the dealio is.

# ¿ Nov 6, 2008 22:01

Delta-Wye: Sep 29, 2005

So I have a lithium-ion question. Well, the batteries are really lithion-ion polymer, but I don't think that really matters for what we're doing. Basically we need two cells in series to generate the voltage we need, and the cells that have the proper x-y dimensions don't have nearly the mAh rating we need. We have a bit of height space to play with, so the current idea is to put two sets of five parallel cells in our robot. We were hoping to have a proper charge circuit this time around instead of using lovely ghetto charging via lab power supply. The charge chip I was thinking about using is the TI bq2006 charging chip, which supports 2-cell configurations. For our purposes (basically we're not making a hundred thousand units that have to work 100% of the time in end-users hands), will it matter that each cell is formed out of a few in parallel? I'm tired of having to make battery packs after the old one goes all preggers on us, and the charging circuit is one step in the right direction as far as fixing the power subsystem for the robot goes. The rest of it I'm confident I can handle, but the li-ion stuff is a bit out of my knowledge area.

# ¿ Jan 25, 2009 00:34

Delta-Wye: Sep 29, 2005

Paul MaudDib posted:

For starters, lithium ion batteries are rather different from lithium polymer.

For the record, we're using small versions of the following:
http://www.sparkfun.com/commerce/product_info.php?products_id=731

I think we've been ordering the batteries (bit smaller, bit cheaper, smaller mAh rating I believe) from some chinese website and soldering up the packs ourselves.

Paul MaudDib posted:

What you're talking about is 100% possible. You can make a pack with a series-parallel configuration no problem. However, you will eventually have cell balance issues. Lithium Polymer batteries have a tendency to charge up to a little different voltage than their peers in a pack, and over time they start to really drift. One cell will be 100% charged, another will be 95%, another will be 97%. That kind of thing. You'll start losing capacity and current rating over time unless you balance them. My father has the chargers to do this for his R/C stuff, they're about $50.

I am aware of the balancing issue. I think we've decided that this is alright - they only have to last 10 minutes at a shot anyways, so we have quite a bit of breathing room really.

Paul MaudDib posted:

You would really really be better off to buy a real charger like a Triton or one of FMA's.
You're probably going to have $100 per pack real fast. Take care of them.

That's not a bad idea, and is more or less what we've been doing. Ideally we don't want to have to haul something down to compete with us, we were hoping to get to the point where we just need a wallwart to charge the robot via a DC barrel connector.

What has really been catching us with our pants down is that voltage requirements have changed since the last iteration of the circuit board, so the regulators were moved into the battery pack. The trickle-discharge from Iq on the regulators over discharges the batteries over breaks from school when they don't get topped off regularly. I'm working on moving the regulators to the board (along with other mods) cause thats loving dumb and I'm tired of dealing with it, and figured it would be a good opportunity to integrate a charger into the design.

Not to mention I would like to have some more experience with li-ions than just rebuilding the packs constantly. *sigh* Thanks for the info so far!

clredwolf posted:

Quoted for truth, Metcal irons are incredible.

Seconding for truth, some of the U's labs have metcals and they are pretty kickass. Buy cheap, buy twice. Stuff like soldering irons should really be an investment.

# ¿ Jan 25, 2009 09:34

Delta-Wye: Sep 29, 2005

Paul MaudDib posted:

If you wanted you could wire a DC barrel connector. The process would just be plug in connector, hold down button for two seconds on a Triton.

Those cells are cheap, yup. Are they just an electronics pack?

I'm really curious what your space restrictions are that you can't use a larger pack but you can use a parallel array of small cells. Usually the larger cells are denser. I'm guessing this is FIRST or something and it's a cost issue?

I might make footprints for a charging chip, give it a try, and if it fails miserably, pull the components off and wire the DC jack as a charging input. We have, in the past, used a DC supply set with a voltage limit of 4.2*# of cells, and a current limit of Capacity*C rating (minus a bit of safety). At first it does constant current at whatever the rated charging speed is, then switches to constant voltage once the cells get closed to topped off. It worked, but we did see significantly lowered life on the cells over the course of a semester. Was never sure if this was because of the charging method being a bit rough or the cells becoming misbalanced.

To let the cat out of the bag, it is a micromouse, and the board (the circuit board is used as the main chassis) footprint is relatively small. We have just enough room on either side of the motor packs for the small cells to get the required voltage, but can stack them as high as necessary to get the required runtime. This would be the only situation I've seen where the flatpack li-ions are not ideal, but they can be made to work.

# ¿ Jan 25, 2009 21:07

Delta-Wye: Sep 29, 2005

SNiPER_Magnum posted:

I'm thinking of making an IC FM radio, but I don't know where to start. I'd like AM too but it's not critical if it will be very complicated. Definitely need stereo. I really want search tuning and to be able to control it using a microcontroller (probably PIC24). The end goal really is to be able to press a button to search up and down for a station and store some presets.

Anyone had any experience with FM radio ICs? I pretty much have none. Suggestions?

http://www.sparkfun.com/commerce/product_info.php?products_id=8972

Typically you can't go wrong with Sparkfun. Example code and all the other goodies.

# ¿ Jan 26, 2009 01:10

Delta-Wye: Sep 29, 2005

Snaily posted:

By the way, is there a trick to knowing what all the xN-series diodes and transistors do, or is it a matter of learning specs by heart? I am going to need some kind of MOSFET to drive my stacks of LEDs, but finding a suitable one that is cheap is like finding the proverbial needle...

In my experience it is mostly just learning ones over time - as you get familiar you know the standard components for each job. Assuming your LED stack isn't insane, a standard 2n7000 or 2n7001 should be fine. If I ever have a situation where I need weird specs (high Id current, unusually high Vce, whatever) it's a matter of going to Mouser and typing in the specs and seeing what comes out.

EDIT: One of my professors was regaling us with stories of the good ol' days and apparently she used to have books of datasheets in the bathroom that she would read while on the can. When she needed a particular component she would have to go back through the datasheets she's read by memory and see if she could remember any useful components. Us dang kids and our internets! :argh:

Delta-Wye fucked around with this message at 00:41 on Jan 28, 2009

# ¿ Jan 27, 2009 22:59

Delta-Wye: Sep 29, 2005

Hillridge posted:

Oops, I was thinking backwards. I should have asked what levels your micro wanted.

One thing to watch out for, especially this time of year, is ESD. Always ground yourself before handling ICs. It's easier than you think to kill a chip with a static shock.

This is especially true in Fairbanks this time of year.

# ¿ Feb 4, 2009 19:14

Delta-Wye: Sep 29, 2005

All About Trout posted:

People are doing cool things with those avrs, like making their own little nes-esque game systems. I'd love to make one to generate random video from some tiles and effects but it seems like a lot of work. I guess I'd be going off of something like this: http://avga.prometheus4.com/

quote:

"The AVGA instantly turns any Mega AVR to a powerful* game console."

Fixed.

All joking aside, that is a neat idea. I build a pong-like copy for fun on a FPGA a while back - vhdl is a bitch in my opinion, but you can do some pretty badass stuff on an FPGA if you know what you're doing.

# ¿ Feb 27, 2009 01:48

Delta-Wye: Sep 29, 2005

Cross_ posted:

Since you mentioned FPGAs, I almost picked up one of these boards last year:
http://www.digilentinc.com/Products/Detail.cfm?NavTop=2&NavSub=423&Prod=S3EBOARD

That is actually the board I built the pong clone on. The VGA connector was just begging to utilized :science:

# ¿ Feb 27, 2009 08:48

Delta-Wye: Sep 29, 2005

I am looking for some easy projects to do for a Eagle layout tutorial my IEEE student branch is considering putting on. The idea is have a few sessions over a couple weeks where we design something, do the layout, order it, and do a soldering party on the last week so people can take home their projects. I think this would be fun, and am just trying to brainstorm some easy/simple/cheap but worthwhile projects.

Some ideas so far -

Simple LED blinker/RGB color shifter, something easy and nice looking, but not relatively useful or technical.

Maybe little keychain flashlights (maybe even that white LED circuit from earlier!), although this would probably require a enclosure of some sort.

TV-B-Gone - One of the IEEE members really wants to do a soldering contest ("speed soldering") and she thought this project would be awesome; whoever turns off the TV first wins... something.

The goal really is to find the most interesting and complicated device we can find that will fit in less than a 1"x1" space. I am trying to balance the desire for a challenging layout with the desire for an easy project as I don't want to get bogged down on details, and having something cool and useful would be a plus.

What say you EE goons?

All this FPGA talk is making my eepenis feel very small... and yet, very hard :awesome:

# ¿ Feb 28, 2009 04:19

Delta-Wye: Sep 29, 2005

ANIME AKBAR posted:

okay, in all honesty you need to take a step back and do some more research on how amplifiers work. I can guarantee this circuit won't perform the way the simulator indicates, since the falstad simulator doesn't take a lot of things into account. It assumes that FETs will be operated under certain conditions, which you're not.

I was actually under the impression we were being eetrolled.

# ¿ Mar 16, 2009 21:06

Delta-Wye: Sep 29, 2005

Mill Town posted:

I'm in need of a logic analyzer that can do up to 500kHz (fortunately I only need 2 channels, I'm analyzing a proprietary serial protocol). Can anyone recommend a PIC or AVR based solution? I've seen a few plans on the Internet but I'm not sure what's good. It needs to be able to store a lot of samples (at least a few seconds worth) and I don't know which design to pick. Thanks!

Sparkfun sells [what sounds like] a really nice USB Logic Analyzer, which is overkill for what you're doing now but it might be worth investing in for the long run. I know I've been looking to invest in one since I first saw it.

hobbesmaster posted:

The HC11 is the best microcontroller in existence.

Do I know you? That is one way to get me all riled up - I'm currently taking a HC12 (9S12) based course and really, goddamn, it most certainly is not the best microcontroller in existence.

The 90s called, and they want their cutting edge processor designs back.

# ¿ Mar 17, 2009 04:02

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# ¿ May 4, 2024 04:52

Delta-Wye: Sep 29, 2005

hobbesmaster posted:

90s? More like 70s. You just have to get into the 70s mindset of CISC and whatever was logical to Motorolla engineers. Its rather... annoying to get into that mindset when you're used to RISC architectures from the 80s/90s such as PIC and AVR. Different things made sense in the 70s than do now.

Yes, an architecture with two registers and a million instructions is not a good design :argh:

EDIT: Wait, there are three registers! But the third points at the first two so whatever

Delta-Wye fucked around with this message at 23:48 on Mar 17, 2009

# ¿ Mar 17, 2009 23:41

The Something Awful Forums > Discussion > Hobbies, Crafts, & Houses > Learning electronics: Release the Magic Blue Smoke

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