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mAlfunkti0n posted:Just checking in, need some advice on a soldering station. For $15, this is a great station: http://www.mpja.com/viewallpict.asp?dept=461 We use them to teach soldering workshops, and they've held up for 2 years without a problem. For $50, this knock-off is great: http://www.mpja.com/prodinfo.asp?number=15141+TL This is the iron I use for everything, from through-hole to leadless surface mount, and it's held up great.
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Oct 28, 2010 14:19
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Zuph posted:For $15, this is a great station: http://www.mpja.com/viewallpict.asp?dept=461 Really interested in the 302A, can you find the tips locally or pretty much just through that site? Edit : Bought one 
mAlfunkti0n fucked around with this message at 16:24 on Oct 28, 2010 |
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Oct 28, 2010 16:14
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mAlfunkti0n posted:Really interested in the 302A, can you find the tips locally or pretty much just through that site? Absolutely can't buy tips locally, but you can get them from MPJA, and https://www.web-tronics.com. I think some Hakko tips work, as well, but I can't promise anything.
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Oct 29, 2010 01:49
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Could it be the same knock-off manufacturer that makes the Aoyue line of soldering stations? Apart from the temperature knob it looks identical. I have an Aoyue 937 and I use Hakko tips with no problem.
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Oct 29, 2010 18:49
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Anybody have any tips for soldering boards with groundplanes? I have a small PCB with a groundplane I am soldering. I am not sure if it is better to go with a higher temperature or longer contact time for the pins connected to the plane. I generally keep the iron at 250 degrees C.
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Oct 29, 2010 19:21
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250C? I generally solder at 350-400C and go up to 450+ for special cases (aluminum PCBs being a common one).
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Oct 29, 2010 19:26
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Yeah I guess maybe it's a tad low. I'm not sure how sensitive components are when soldering, so maybe I've been having too low temp.
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Oct 29, 2010 19:37
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Typically, not very sensitive - you usually worry more about ESD than heat when doing manual soldering. It'll also be on most ICs' datasheets if you're really worried about a particular component, the temperature and duration for both manual and reflow soldering. I wouldn't worry about it much. Having it hot will let you solder much faster and easier as you get better at it.
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Oct 29, 2010 19:48
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Just stick an alligator clip or other heatsink on or near the component. It helps keep the rest of it cool.
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Oct 30, 2010 00:57
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Zo posted:If you're soldering for yourself (instead of at work where it's banned) there's no reason to EVER use lead-free solder. I dunno, my (completely unscientific) impression from using lead-free solder for the last few years is that it isn't that bad as long as you bump your temperatures up a bit. Strangely though, i've found this is only the case on FR4, lead-free on metal clad boards can go suck a dick as far as i'm concerned.
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Oct 30, 2010 15:55
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Captain Birdseye posted:I dunno, my (completely unscientific) impression from using lead-free solder for the last few years is that it isn't that bad as long as you bump your temperatures up a bit. Strangely though, i've found this is only the case on FR4, lead-free on metal clad boards can go suck a dick as far as i'm concerned. Lead free on metal boards... Sounds a lot like my last job. You wouldn't happen to be in the LED lighting industry would you?
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Oct 30, 2010 17:46
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SnoPuppy posted:If you need to make measurements of a higher voltage, just use a resistor divider to scale the voltage down. I tried this but I get significant noise when the voltage changes. Since my circuit deals with square waves and short pulses it kind of is completely useless. I saw somewhere that if I added capacitors that it would help reduce the noise, but then I get distortions as these capacitors are charging(the capacitors are small plasic blocks which say 10nJ100, I've tried every type I have and those seem the best). Can anyone offer any advise. I've attached a picture of what I tried, the important bit is the bit at the bottom. Currently I'm testing the output by connecting it to myself and seeing how much it contracts my muscles. I don't think this is the best way to test my circuit, especially with my limited electronics knowledge. My oscilloscope is a picoscope 2104, the max voltage it can measure is 20V, I want to measure up to 100V.
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Nov 1, 2010 22:36
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Unparagoned posted:I tried this but I get significant noise when the voltage changes. Since my circuit deals with square waves and short pulses it kind of is completely useless. I saw somewhere that if I added capacitors that it would help reduce the noise, but then I get distortions as these capacitors are charging(the capacitors are small plasic blocks which say 10nJ100, I've tried every type I have and those seem the best). Can anyone offer any advise. I've attached a picture of what I tried, the important bit is the bit at the bottom. I'm having a hard time understanding what you drew. When you say short pulses, how short are you talking about? What is the rise time? How much noise is "significant"? Just for reference, your probe should be hooked up like this: Input Signal------\/\/R1\/\-----Probe Here-----\/\/R2/\/\-----Ground
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Nov 1, 2010 23:00
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SnoPuppy posted:I'm having a hard time understanding what you drew. I think I had it like Input Signal-----Probe Here----\/\/R1\/\-----Ground So I need a resistor connected to both the input and ground, rather than just at either the input or ground?
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Nov 1, 2010 23:23
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Unparagoned posted:I think I had it like Yes, that way the power is actually divided. Your resistor values should also be sized such that they don't affect your circuit (if you pick something like 100/500 ohms you might have too much loading, which would affect the circuit). You also want to make the resistor-probe-ground junction as small as possible, to avoid ground loops and parasitic effects.
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Nov 2, 2010 00:31
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Unparagoned posted:I think I had it like Yes, that's where the divider part comes in. If you have two resistors of equal value, the voltage between then will be 1/2 the input signal - they divide the signal in half, effectively, as each drop an equal portion of the voltage.
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Nov 2, 2010 00:31
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SnoPuppy posted:Yes, that way the power is actually divided. Your resistor values should also be sized such that they don't affect your circuit (if you pick something like 100/500 ohms you might have too much loading, which would affect the circuit). Doh, so literally I just use a voltage divider. It seems weird connecting various parts of the circuit to the ground through resistors. I'm using 2MOhm resistors, so I assume they should be high enough so it doesn't effect the circuit much. One question is there any reason to use lower resistors? Thanks all for the help, I was considering buying a new oscilloscope. I guess I can put that off for a bit now. For reference I had it connected like this before. It worked but was noisy. Input signal----probe. Probe ground connection----R1---Ground.
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Nov 2, 2010 23:27
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Unparagoned posted:Doh, so literally I just use a voltage divider. It seems weird connecting various parts of the circuit to the ground through resistors. I'm using 2MOhm resistors, so I assume they should be high enough so it doesn't effect the circuit much. One question is there any reason to use lower resistors? Er, make sure the probe ground connection is directly connected to ground. The issue with resistor dividers where the resistors are too big is you're actually forming a divider with three resistors - the two actual resistors, and the probe. If the divider values are of the same magnitude of the probe, you have to calculate the divider value with the lower leg formed by the actual resistor in parallel with the probe. The rule of thumb is two resistors in parallel have a value less than the smallest resistor. If the smallest resistor is much smaller than the other, the value should be close to the value of the smallest - as the larger approaches infinity, this approximation becomes exact. At 2Mohm you might see some loading effects from the probe, but it that may not matter in your application.
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Nov 3, 2010 01:50
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If capacitance is the same, is it OK to replace a capacitor with one of the same type and a higher voltage rating?
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Nov 3, 2010 19:41
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GWBBQ posted:If capacitance is the same, is it OK to replace a capacitor with one of the same type and a higher voltage rating? Yes. Voltage rating is the maximum that a capacitor can be subjected to before the dielectric breaks down, but below that it doesn't make a bit of difference.
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Nov 3, 2010 20:47
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BattleMaster posted:Yes. Voltage rating is the maximum that a capacitor can be subjected to before the dielectric breaks down, but below that it doesn't make a bit of difference. Additionally, if you're using ceramic capacitors, you *want* to have a higher voltage rating because their capacitance degrades with DC bias. For example, a 10v X7R capacitor will loose 25% of its capacitance when you use it on a 5v rail. If you actually use it at 10v, you will loose up to 60% of the rated capacitance.
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Nov 3, 2010 22:25
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That's what I thought on voltage, and good to know about capacitance loss, but this is an aluminum electrolytic so it's not a concern at the moment.
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Nov 3, 2010 22:51
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SnoPuppy posted:Additionally, if you're using ceramic capacitors, you *want* to have a higher voltage rating because their capacitance degrades with DC bias. Oh huh, I didn't know ceramics acted like that. I'm pretty sure it doesn't matter for electrolytics though.
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Nov 4, 2010 01:13
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BattleMaster posted:Oh huh, I didn't know ceramics acted like that.
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Nov 4, 2010 07:19
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Any distributor is fine as long as they don't have absurd minimum order quantities (I just want one or two) and they're not some ultra obscure asian outfit that only does business in chinese or something. Also they have to clearly list the price and give a reasonably precise shipping time (non of those sites where you order by placing a request for quote, then hoping they don't gently caress you later on). Also, I've already ordered a couple through LEM's own website, but they probably won't be here for a long time, so LEM's site doesn't count. edit: I'd also be willing to settle for the lower current equivalent model, the LAH 50-p, if the 100-p can't be found. Edit2: holy poo poo, they just got 2000 more in stock just after I posted this. Nevermind!! ANIME AKBAR fucked around with this message at 18:01 on Nov 4, 2010 |
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Nov 4, 2010 13:17
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Are there any tips on reverse engineering a circuit? Say a simple PCB with both tracks visible.
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Nov 4, 2010 20:32
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Unparagoned posted:Are there any tips on reverse engineering a circuit? Say a simple PCB with both tracks visible. When you say both tracks...you're talking literally two traces? Or that you can see both top and bottom traces? The biggest thing is that if you are trying to read component values (especially resistors that you can't read the print on or capacitors) you'll probably need to remove them from the circuit to get accurate measurements of their values. Do you have a picture of what you're trying to break down?
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Nov 5, 2010 02:29
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Are there formulas for: -Wattage w/ respect to frequency for a given waveform -Converting wavelength to frequency and vice versa The context I'm dealing with here is, say, this example: At radioshack I found some LED's. They are measured in wavelength (i.e. 400 nm), current, and milliwatts. Here's two completely arbitrary values that I'm making up off the top of my head: 650 nanometers at 4000 mw and 400 nm at 650 mw. Say, hypothetically I wanted to make a dooms-day weather controlling laser beam. For example. I'm trying to figure out if 4000 mw at a wavelength of 650 nm would yield a greater overall "intensity" (I'm not even sure if that's the correct term). I'm sure you could also see plenty of other implications for knowing these formulas. TIA
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Nov 5, 2010 04:55
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The Scientist posted:Are there formulas for: For a given waveform, wattage is still voltage*current, it's just voltage and current are no longer constant numbers. What kind of waveform are you talking about? Usually you need to integrate the wave form to figure it out. To convert from wavelength to frequency, you need to know the speed of propagation. Since you're using light, this is easy. http://zebu.uoregon.edu/~soper/Light/frequency.html wavelength = c/frequency = (3 x 108 m/s)/(Hz) Keep in mind that effective light is not just a factor of the brightness of the source and the frequency, but the amount of light reflected by the surface you're shining it on. Think black tshirt on a sunny day.
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Nov 5, 2010 05:18
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Thanks for your reply, that does clear things up somewhat. I guess if we're talking an LED, would that be emitting a sinusoid?
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Nov 5, 2010 06:45
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The Scientist posted:Thanks for your reply, that does clear things up somewhat. Ugh. Huh. I'm sure someone will come in here and show me up, but usually the light emitted and the electrical power are considered separately and it sounds like you're asking if the light emitted is a sinusoid? If you bias an LED properly, it turns on and emits light. The light is a result of electrons jumping from the cathode to the anode and recombining there. I'm not clear on the physics, totally, but the light frequency is a result of the material (wikipedia specifically indicates the 'energy gap' is the factor at play). If you run a constant current through the LED, it emits light at a certain frequency. The light is constant, but I guess something must be varying to get the particular color, and that must be a frequency of some kind. You know, I've never thought about what form the light actually is  Keep in mind even stuff like a pure sinusoidal tone only looks like a sinusoid when you graph pressure v. time at one point, due to the fact it's a longitudinal pressure wave. Would the color just be a matter of how fast photons are released? Faster = higher frequency? Just a guess though. Now I'm curious as well!Keep in mind thats with a constant-current biased LED. If you drive an LED with a sinusoid, it will only be 'on' during half of the wave form, and the light will vary in brightness and not color. Unless you run too much current through it. Then it gets real pretty for a split second, and then dark forever more.
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Nov 5, 2010 07:59
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Delta-Wye posted:You know, I've never thought about what form the light actually is Higher energy = higher frequency. Planck's law, and whatnot. Brightness is number of photons/sec. As far as any of the rest of it goes. Color temperature vs apparent brightness is a factor of "chrominance" and "luminance." Check into the wikipedia articles about chrominance, gamut, pure color spectrum, and the frequency response of the various light-gathering cells in the eye. Mostly, green seems "brighter" for a given luminance (photons/sec) than red or blue. No LED gives a "pure" color (one that is centered on, and has the frequency response distribution of a color receptor in the eye).
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Nov 5, 2010 12:11
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GWBBQ posted:That's what I thought on voltage, and good to know about capacitance loss, but this is an aluminum electrolytic so it's not a concern at the moment. This probably doesn't apply to you, but make sure your cap isn't a special low ESR type. I've found that these tend to have lower max voltages and replacing them with a higher voltage, higher ESR cap may lead to undesirable results.
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Nov 5, 2010 14:37
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The Scientist posted:Thanks for your reply, that does clear things up somewhat. All light emitted is a sinusoidal wave. It's just not at a number we can use. A standard red LED emits light at roughly 650nm. Dividing C by 650nm gives us a frequency of 46,100,000,000,000,000 Hz (I may be off by an order of magnitude, but ... still). If you are modulating the light by any kind of shaped wave, the amplitude of the sine wave will match the modulation you put into the diode.
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Nov 5, 2010 14:52
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Thanks guys. But let me further muck things up. Let's stick with my "theoretical" doom's-day laser. So we all know that you should never stare directly at the sun, or the flash from a nuclear bomb exploding, or the arc of an arc welder. But what specific measurable attribute is it about an arc welder that makes the beam hazardous to look at? You can look at the spark from a piezoelectric ignited lighter, no problem. Or, say, a Jacob's ladder. But a welder needs to have enough intensity that it can melt metal and send molten particles from one pole at the end of the welding stick to the material surface, of opposite polarity. Would we say that the danger of looking at an arc welder's arc grows with the wattage that is flowing across the gap and through both metals? Like a lightbulb? Back to my LED laser. One of my problems, you guys have solved for me. Higher frequency = higher energy. (Although I was kind of hoping for some kind of formula whereby I could compare two LED's, one of higher wattage but lesser frequency/greater wavelength, and one of lesser wattage but higher frequency/lesser wavelength). But what measurable trait, specifically, pertains to how "powerful" (I am having a hard time coming up with an adjective that doesn't already imply a measurable trait [power = watts, intensity = lumens, apparently, transferable energy is seemingly a function not only of the LED and the light it emits but also of the surface the focused light is interacting with]) a focused laser beam would be. So I'm in radioshack, standing in front of the components cabinet, looking at LEDs. I would want to find the LED's with the most, what? Wattage? Smallest Wavelength? Greatest intensity in Lumens? (keep in mind that at this point, this is still kind of a thought experiment. I'm aware that no LED would make anything close to a laser beam on its own, and without focusing.)
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Nov 5, 2010 17:59
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TacoHavoc posted:When you say both tracks...you're talking literally two traces? Or that you can see both top and bottom traces? Both tracks as in both top and bottom traces. I'm not actually too concerned about the values of parts. I'm mainly concerned on seeing how they the circuit works in general. So the main bit would be to draw a circuit diagram. I have a few circuits that kind of do the same thing but in different ways. Here is one. edit: The chip doesn't do any complicated fancy stuff.
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Nov 5, 2010 18:46
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The Scientist posted:Thanks guys. But let me further muck things up. Arc welding puts out a tremendous amount of UV light; UV light is pretty dangerous to your eyes and at the brightness arc welding puts out, very dangerous. If you wanted to do eye damage, an array of UV LEDs at pretty high brightness would slowly blind someone and they would have no idea because the LEDs would look off. To get that brightness, you'd want something that has a color output outside of the visible range, and output brightness (usually measured in candelas or lumens) that is high enough to do damage. You could vary the brightness from maximum to off by changing the current through the LED (effectively, the wattage). I'm hoping you aren't a tremendous dick.
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Nov 5, 2010 18:54
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Delta-Wye posted:I'm hoping you aren't a tremendous dick. No that would be horrible. It just seemed like a good example of light transmitting energy like a laser. If the sun's corona transmits energy enough to blind a person during a solar eclipse, in that one specific instance those particular circumstances seem like a good analog for a laser. One that can do damage after 8 light minutes of travel and then through our earth's magnetic fields and the ionosphere and the stratosphere and the atmosphere etc. etc... But again thank you.
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Nov 5, 2010 22:48
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Unparagoned posted:Both tracks as in both top and bottom traces. I'm not actually too concerned about the values of parts. I'm mainly concerned on seeing how they the circuit works in general. So the main bit would be to draw a circuit diagram. I feel like I know what that goes to, but just can't quite place it. As for reverse engineering, I've done this before and it can be a pain in the balls. A 2 layer PCB isn't too bad to get the interconnections from since you can see where they all go. A multimeter will help double check that. Some of those 3 terminal devices may be difficult to figure out though. They usually aren't marked well and could be single diodes, double diodes in a variety of configurations, transistors, etc. There are a few places that list the codes found on these packages, but some are shared and they aren't easy to match up. Since that big chip is the central point on the board, the datasheet for the chip may give you insight as to what the rest of the parts are doing.
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Nov 6, 2010 04:08
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Hillridge posted:This probably doesn't apply to you, but make sure your cap isn't a special low ESR type. I've found that these tend to have lower max voltages and replacing them with a higher voltage, higher ESR cap may lead to undesirable results.
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Nov 6, 2010 05:20
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