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Wow, the Arduino stuff moves fast. A few months ago I'm 90% sure the SPI interface stuff was just not there, now there's at least 3 tutorials up on how to interface using Arduino SPI. I'm so stoked, too bad it invalidates a lot of my project (stupid PIC32)... Hopefully the Arduino SPI is a half-decent speed (I'd be happy at 1MHz). If not...that's what special crazy overclocking is for, heh heh... Anyone messed with Arduino SPI code before? What's the speed like, if you can tell? Also, I've mentioned off and on this crazy project I've been wasting my life away on. I'll post a thread on it when I feel like it's ready for photo-ops. That may be a few months away, but I may drop a few hints on this thread here and there if anyone is interested. For now: code:
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Jan 23, 2009 00:00
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ok this has been bothering me for a while, but do we have any kind of good tutorial on soldering Iron maintinance. My Iron gets this horrible black poo poo all over it and refuses to have anything stick to it really fast. I keep it tinned when it's off and I clean it frequently, but I end up having to literally scour it between uses, and even then I can only use it for like 1 hour before it becomes completely crap.
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Jan 23, 2009 18:01
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Zaxxon posted:ok this has been bothering me for a while, but do we have any kind of good tutorial on soldering Iron maintinance. My Iron gets this horrible black poo poo all over it and refuses to have anything stick to it really fast. I keep it tinned when it's off and I clean it frequently, but I end up having to literally scour it between uses, and even then I can only use it for like 1 hour before it becomes completely crap. is it black like melted plastic, or is it semitransparent brown goo? if the latter, it's probably excess rosin. and it's pretty normal to have to sponge a tip every five minutes or so. you're using a wet sponge, right?
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Jan 23, 2009 18:32
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mtwieg posted:is it black like melted plastic, or is it semitransparent brown goo? if the latter, it's probably excess rosin. it's black and brown, so I'm guessing the rosin. And yeah I use a sponge.
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Jan 23, 2009 20:39
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Zaxxon posted:ok this has been bothering me for a while, but do we have any kind of good tutorial on soldering Iron maintinance. My Iron gets this horrible black poo poo all over it and refuses to have anything stick to it really fast. I keep it tinned when it's off and I clean it frequently, but I end up having to literally scour it between uses, and even then I can only use it for like 1 hour before it becomes completely crap. What have you been scouring it with? I use a wet sponge to clean mine every few joints when stuff is just starting to build up. Every once in a while I use a plain copper pan scrubber with no soaps in it to get some of the more stuck bits off. Also to keep the tips lasting longer keep a coating of solder on the tip when stored or stopping for a while. It might be a case where the coating on your tip has oxidized a bunch.
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Jan 23, 2009 21:00
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ValhallaSmith posted:What have you been scouring it with? plain copper pan scrubber.
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Jan 23, 2009 22:07
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What kind of iron do you have? When was the last time you bought a new tip? I never had very good luck when I had a cheap non-temperature controlled iron, the tips would oxidize away before your eyes.
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Jan 24, 2009 03:10
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I have 2 irons. Both of them sub 100 but both somewhat temp controlled (dials with 1-2-3-4 on them) both do the same drat thing. My friend eric uses a cheap $25 iron and it never seems to give him any poo poo, which makes me think I'm doing something wrong with them. I tend to only have to turn the heat about halfway up to get the solder a meltin'. But that starts the iron crappin out.
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Jan 24, 2009 03:20
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How old is the tip? How often do you use it? Are you actually scouring it with copper? Or just lightly rubbing it down? Where is the black? On the heating surface or above it?
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Jan 24, 2009 03:43
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Bexx posted:How old is the tip? How often do you use it? Are you actually scouring it with copper? Or just lightly rubbing it down? Where is the black? On the heating surface or above it? one Iron I have had for about a year and the other is brand new, the black is on the heating surface. though it's more brown close to the end. Normally when using the Iron I heat it up and let it sit. Then I melt a little solder on it to see if it's hot enough, after that I wipe the iron off on a damp sponge and then I solder things, wiping the Iron down a bit when I'm not using it directly (usually once every couple of minutes.) Then when I'm going to put it up, I melt a little blob of solder to the end and shut it down. After a couple of sessions, the black crap has build up so much that nothing will stick to it. So I take the copper pan thing (I have one only to this purpose, never used for anything else) and scrape the crap off. That gets it right to use again until about a year.
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Jan 24, 2009 04:12
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Zaxxon posted:one Iron I have had for about a year and the other is brand new, the black is on the heating surface. though it's more brown close to the end. Get it hot. Slap some flux on it. Rub it hard on a wet sponge, still hot. Repeat a few more times. See if that is any better. You may have too much resin in your flux/solder and your just getting a gunky build up. You can also try cranking the heat all the way up to see if you can burn it off. You should also check is closely to make sure you haven't marred up the surface. A scratched up tip won't conduct heat as well so stuff will flow towards it and stick on. If I were you I would think about using some cleaner materials though. And getting a Metcal soldering iron cause they loving rock. And they aren't nearly as expensive as they used to be either.
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Jan 24, 2009 06:31
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Zaxxon posted:...after that I wipe the iron off on a damp sponge and then I solder things, wiping the Iron down a bit when I'm not using it directly (usually once every couple of minutes.)... This might be your problem. Are you leaving it tinned while it's sitting idle? Or are you wiping it down periodically, leaving it bare? You don't want it to sit there hot with no solder on it, that's when the tip can oxidize. If you're not already doing so, make sure you melt some solder onto the tip after each time you wipe it.
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Jan 24, 2009 09:26
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Bexx posted:And getting a Metcal soldering iron cause they loving rock. And they aren't nearly as expensive as they used to be either. Quoted for truth, Metcal irons are incredible. High quality Weller irons are pretty good too, I like Metcals much better for fine work though. Chaning the tips is so, so easy (just don't EVER trust them to be cool).
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Jan 24, 2009 21:05
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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.
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Jan 25, 2009 00:34
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Does anyone know a good way to adapt a surface-mount chip to a DIP format? I found a programmable function generator (AD9833) that would be perfect for my current project, but it is a surface mount chip which makes it hard to breadboard. Adafruit has a prototyping shield that can handle one SOIC device, but I would have to solder the chip to the board, it's an option but not an ideal one since I'd have to plug into that shield every time I wanted to use that particular chip.
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Jan 25, 2009 04:01
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PDP-1 posted:Does anyone know a good way to adapt a surface-mount chip to a DIP format? I found a programmable function generator (AD9833) that would be perfect for my current project, but it is a surface mount chip which makes it hard to breadboard. You could dead-bug the chip:  (Not mine, from: http://macetech.com/blog/node/23) Or buy something like this from SparkFun: http://www.sparkfun.com/commerce/product_info.php?products_id=494
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Jan 25, 2009 05:00
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As mentioned above, sparkfun has a few different surface to dip adapters. You could also check out Schmart boards: http://www.schmartboard.com
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Jan 25, 2009 05:02
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Delta-Wye posted:li-po questions For starters, lithium ion batteries are rather different from lithium polymer. 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. 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.
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Jan 25, 2009 07:04
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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. 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.
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Jan 25, 2009 09:34
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PDP-1 posted:Does anyone know a good way to adapt a surface-mount chip to a DIP format? I found a programmable function generator (AD9833) that would be perfect for my current project, but it is a surface mount chip which makes it hard to breadboard. well first of all this device comes in an MSOP package which is much smaller than SOIC. It's feasible to dead bug solder it but it's quite difficult and really requires the right type of wire (Teflon insulation). It will be fragile and a pain in the rear end. You can find breakout boards made for this kind of stuff. They're pcbs with surface mount footprints attached to through holes that are easy to solder to. Finding one for an MSOP package might be hard though. A friend of mine once found the website of a place that specialized in breakout boards. I'll try to get it from him.
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Jan 25, 2009 09:54
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Thanks for the responses everyone. I didn't know break-out boards existed, but it makes sense. Knowing what to Google for turned up epboard.com which seems to specialize in converting every kind of pin format to DIP so that you can breadboard it up.
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Jan 25, 2009 14:42
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Delta-Wye posted:For the record, we're using small versions of the following: 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?
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Jan 25, 2009 18:29
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ANIME AKBAR posted:well first of all this device comes in an MSOP package which is much smaller than SOIC. It's feasible to dead bug solder it but it's quite difficult and really requires the right type of wire (Teflon insulation). It will be fragile and a pain in the rear end. You can find breakout boards made for this kind of stuff. They're pcbs with surface mount footprints attached to through holes that are easy to solder to. Finding one for an MSOP package might be hard though. A friend of mine once found the website of a place that specialized in breakout boards. I'll try to get it from him. digikey has an MSOP to SIP converter. But it seems to be 8 pins only. http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=33108CA-ND
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Jan 25, 2009 19:20
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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. 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.
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Jan 25, 2009 21:07
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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?
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Jan 26, 2009 00:51
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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. 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.
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Jan 26, 2009 01:10
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Unfortunately they are sold out. They have a TEA5767 datasheet there, and I've been looking at TEA57xx chips. The TEA5777 does AM also but has been discontinued. They all look pretty tough to deal with. Now some really fun stuff. Before I looked into the new bigger chips, I was really looking at these: TDA1599 for FM and TDA1572 for AM (PDF datasheets). The 1599 has one audio out pin for MPX. So I'd get my stereo from that? Doesn't sound too bad, I think. They look fairly simple to deal with and build nice radio from. I probably couldn't prototype any of this on a breadboard, could I?
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Jan 26, 2009 03:47
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I'm looking at making a dimmable LED light fixture by making a variable duty cycle square wave with a 555, and I was going to use this circuit. However after running it in SPICE (TINA) the frequency is not constant for a given duty cycle percentage (not even for, say, 90% and 10%)! Do I just suck at simulating, am I missing something (like highly differing source/sink impedances on the output pin), or is the circuit wrong?
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Jan 26, 2009 17:15
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Snaily posted:I'm looking at making a dimmable LED light fixture by making a variable duty cycle square wave with a 555, and I was going to use this circuit. Do you mean that the frequency changes as you adjust the pot (this is normal) or that the frequency changes on its own without adjusting the pot (this is not normal)?
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Jan 26, 2009 18:25
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Mill Town posted:Do you mean that the frequency changes as you adjust the pot (this is normal) or that the frequency changes on its own without adjusting the pot (this is not normal)? Frequency changes as I adjust the pot. I was under the impression that this would not be the case (as stated below the diagram). Or in any case, I thought the frequency should be the same for 10% and 90% duty cycle if not in between.
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Jan 26, 2009 18:43
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Snaily posted:Frequency changes as I adjust the pot. I was under the impression that this would not be the case (as stated below the diagram). Or in any case, I thought the frequency should be the same for 10% and 90% duty cycle if not in between. Normally with a 555, the frequency depends on both the resistors and capacitors, so changing any one changes the frequency. However, looking at that diagram again, it does look like they have designed it a bit differently, perhaps in a way that's supposed to avoid this. Maybe your simulation is wrong, I dunno.
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Jan 26, 2009 19:36
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Mill Town posted:Normally with a 555, the frequency depends on both the resistors and capacitors, so changing any one changes the frequency. I'll mirror the image and paraphrase the argument:  Basically what happens on the left side is that C1 is alternately charged and discharged from/through the output Q, which switches depending on the voltage at TR and THR - the very capacitor in question. Now, the tricky part is that the diodes force the charging and discharging to be done different ways, in such a way that the total resistance in one charge-discharge cycle is constant, supposedly giving a constant frequency. The simulation engine says that the discharging is much faster, however. Hm.
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Jan 26, 2009 23:33
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I don't know how your program is modeling the internals of the 555, but it is possible that the source current and sink current capabilities of pin 3 are different which would lead to the situation you describe. If you set the pot right in the middle so that the charging and decharging curves see 50kOhm each, any difference in the time constants would be due to the internal source/sink impedances of the chip. If that were the case you could balance out the difference by adding a resistor between the pot and whichever diode is conducting during the faster transition. Also check the size of the timestep of your simulation. It needs to be much smaller than, say, 1/(100*C1) otherwise it may overstep the point in the charging curve where pin 3 is supposed to make a transition.
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Jan 27, 2009 01:21
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Snaily posted:I'll mirror the image and paraphrase the argument: Surely the forward voltage drop across the diodes is going to bias the charging/discharging cycles? Try a higher rail voltage relative to the forward voltage drop and see if the frequency becomes more stable with respect to the potentiometer position.
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Jan 27, 2009 06:29
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Was wondering if someone can help me out with a project I'm working on. I'm trying to take the output of a Garmin eTrex GPS and read the data on an Arduino board. To do that, I'm running (or at least trying to run...) the signal through an RS232 to TTL converter to get the signal "understandable" by the Arduino. The circuit I'm using was one I found while doing a google search, and comes from sodoityourself.com. The circuit looks like this...  To even get this to work, I had to replace the capacitor between pin 2 and pin 16 with a 10 uF. And this did seem to work, at least for a while, as detailed here. Only now, it appears that it's only working intermittently, and not at all when I solder it down on perfboard. Is there something inherently unstable about the design on sodoityourself.com, and if so, is there another circuit anyone can recommend?
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Jan 27, 2009 08:10
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Mill Town posted:PDP-1 posted:catbread.jpg posted:While none of these were right per se, I'd like to thank you all for helping me out. Turns out the 555's high output voltage is not Vcc, but ~2.5V lower than it, therefore biasing the switching point of the circuit. I shall try to fit in a transistor to fix this.
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Jan 27, 2009 13:29
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FuzzyBuddha posted:Was wondering if someone can help me out with a project I'm working on. I'm trying to take the output of a Garmin eTrex GPS and read the data on an Arduino board. To do that, I'm running (or at least trying to run...) the signal through an RS232 to TTL converter to get the signal "understandable" by the Arduino. The circuit I'm using was one I found while doing a google search, and comes from sodoityourself.com. I use this chip all the time in designs. What voltage level are the signals from the Garmin? For reference, my applications have 3.3V signals coming into the Maxim part. You mentioned the cap between 2 and 16. That's just a cap from V+ to Vcc. I usually have V+ (and V-) through a 0.1uF 50V cap to ground. Here's my typical setup: Hillridge fucked around with this message at 16:29 on Jan 27, 2009 |
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Jan 27, 2009 16:20
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FuzzyBuddha posted:Was wondering if someone can help me out with a project I'm working on. I'm trying to take the output of a Garmin eTrex GPS and read the data on an Arduino board. To do that, I'm running (or at least trying to run...) the signal through an RS232 to TTL converter to get the signal "understandable" by the Arduino. The circuit I'm using was one I found while doing a google search, and comes from sodoityourself.com. The MAX232 is a 5 volt part. Are you using 3.3 volt supply or logic levels? If so, you want the MAX3232.
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Jan 27, 2009 18:19
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Snaily posted:I'll mirror the image and paraphrase the argument: just a tip, rather than messing with diodes and transistors in the charging loops, an easier way to make a well behaved PWM with 555 is to use two of them. One as a fixed frequency oscillator in astable with a very high duty cycle (so it gives short negative pulses) clocking another 555 in monostable mode. Frequency is completely controlled by the first while duty cycle is controlled by the pulse width of the second, so your duty cycle varies linearly with the potentiometer setting (with the pot being in the astable 555) ANIME AKBAR fucked around with this message at 18:25 on Jan 27, 2009 |
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Jan 27, 2009 18:19
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ANIME AKBAR posted:that's a rather unusual implementation of the 555, though I don't see why it wouldn't work. I got around my problem by using a TLC555. The output is now just the way it should be, at least in the simulator  Dual 555s sound like a technically good solution, but the diode one does seem more fun and potentially slightly cheaper in supplies (by like 10 cents, thanks to the 1N5817 Schottky diodes). Maybe I'll do both.
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Jan 27, 2009 18:51
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