I need some electronics help with an idea I'm having... Can I salvage some knob controls from an old guitar amp and use them to control fan speed and/or led brightness? From a little googling and wikipediaing, it appears that the knobs I see on this dismantled guitar amp circuit board are potentiometers and i think it could work. Would there be too little current to control the fans? And if I can use this, can I use just the knob, or will I need some of the circuitry it's attached to? Thanks!
here's a sticky that has heaps of info. You can just use the knobs with the pots by themselves to control leds & fans, but if you put more than 1 or 2 fans on a single knob, you'll probably burn the knob out, and you can't put more than one led per knob, unless you are happy for them to all work together, like case lighting, and in this case you'd be limited as to how many leds each knob can handle without burning out.
Hey thanks for the link. I'd seen the guides but somehow I missed this page http://forums.bit-tech.net/showpost.php?p=927003&postcount=3 It seems to have just what I need, but it's too late for me to read in depth... my eyes are bleeding from all wild projects I've been reading! Yeah, I basically was planning on switches to just have the lights on and off, and the knobs for fan speed control (individually). Do you know how I can figure out the specs for these amp pots (ie to figure out how many leds it could handle?)
You need to find out how many watts the pots can handle, and what type of leds you are going to power. From there you can figure out how many leds you can control. If you add a cheap transistor, which you may possibly have available on the board you are salvaging parts from, or just spend a tad more and get a high power one, then you can potentially add unlmited leds. If you post pics of the pots with a ruler next to them so we can tell how big they are, or just compare how they look and the dimensions of pots for sale at electronics stores like maplins, then it can be figured out what approximate wattage they are.
pots pics Hey mvagusta, Thanks for your response/tips. Here's pics of the pots (lemme know if that doesn't work, I'm new to this photobucket thing) Preview appears ok. I'm not sure if the one on the right came with just the bare metal, or if that's just the work of the previous owner : They're about 1/2in wide, and maybe a 1/4in thick. edit--- I desoldered the parts pictured from the board... the one on the left has a part number of 71190522, and 1 megaud 9236 written on the bottom- which turns out to be a "1 meg potentiometer, Audio 5% taper, PC mount" according to vibroworld.com. That doesn't help me much, but I figure you'll be able to help. The one on the right, I haven't found yet, but has Alps (not sure) engraved in it as a logo, it's made in Japan, and has the numbers 9222a, 10ka, #528 on it as well. [offtopic] Also, bonus points if you can help me figure out what these switches are. They're pushon/pushoff type, but they seem to be connected to each other so that one will influence the other. I've included the front panel pic to show the context. Edit --- the bottom of the switch says toneluck sicg, and I think I found it on the toneluck site. There's a similar pic calling it a PBN pushbutton switch. Here's the specs: http://www.toneluck.com/pdf/PBN.PDF [/offtopic] desoldered pics:
Those volume controls are pretty small, probably around .1w-.2w, which means they could only control around 2-4 leds each without a transistor circuit, and they'd be too weak to control a fan without a transistor circuit. Pwm circuits as shown in Cpemma's sticky would be best for fans, and i think there's a diode-bus circuit for controlling leds, which is better than using variable resistors aswell. Those linked switches work as they seem, where pushing one button can release the other, but i doubt they'd be of any use to you. If you were to check all the potentiometers with a multimeter, you'd find out how many ohms/kohm/megaohms they all are. You'd need to also read up on ohms & resistors if you want to hook up leds with potentiometers. http://en.wikipedia.org/wiki/Ohm_(unit)
Too weak, eh? What's a megaud? I definitely have a lot of research and testing to do. I found cpemma's website as well, which has some good info... just gotta get up to speed. His explanation of why a variable resistor was a bad idea for leds was interesting and informative. I've been distracting myself with fun stuff like sleeving, and playing around with a few different ideas, but gotta get the circuitry handled as well. I'll keep looking into this, and let you know how I go (or if I have more questions.)
more questions So I've hooked up my old analog multimeter (which I bought years ago at a garage sale, and haven't used beyond to test batteries) to the pot (center and left terminals), and done some testing. Had to change out the 9v battery because I wasn't able to zero out the 10k range with the test leads connected. Once I did that, I was able to zero out that range, and feel confident in the accuracy of the reading. The 2 different pots show quite a difference. The one that says megaud on it (see previous pics to refresh memory) shows a lot more resistance than the other (with the metal back plate.) The megaud (of which I have a few on this circuit board) shows as 70 at the most resistive setting on the 10k range setting. (In comparison, the other barely registers 1 at the 10k range setting, and when dialed down to the 1k range and rezeroed shows as 6). Does this mean that the total ohm resistance (for the megaud) is 70kohm? or 700kohm? And what does this translate to in terms of ohm? IF 70kohm, then that's 70000ohms? And if 700kohm, then 700000ohms? That seems like a lot of resistance… I'm sure I'm off on this though, as that seems to be too high. I must be missing a concept. Sorry to bring you back to electronics 101, but can you help me understand this and also how it fits into my plans for controlling fan speed (without building a transistor circuit, though I’ll do that if I need to)? For example: I've got a case fan, shows 12v, 0.16a, and 1.92 watts on the sticker. As I understand it, my goal in terms of getting slower fan speeds would be to lower the voltage provided to the fan by adding resistance (in this case, hopefully with the above pot) before it gets to the fan. I’m not sure how to use the above info, however, and what to do next to figure it out (or to go the next step and control 2 fans at the same knob. (sorry, but I’m being lazy, and multitasking with a few other projects as well.) Just for giggles, I hooked up the megaud pot to an old fan, and tried it out. I see now why pwm is good, I believe, as the knob on the pot could only make a small adjustment before the fan stopped spinning. (It’ll spin again if I turn it up, but I’m not able to get the fine control on the fan as I wanted.) Any help/ideas appreciated.
You know how i said they are too small & weak to control a fan without a transistor, well that's because they can't handle nearly 2 watts going through them, they wouldn't last long with .5 watt going through them! You said you hooked up the fan for a moment and it was easy to stop. Did you smell anything burning? If not, then the pot would have been close to it, well the resistive track on the inside anyway. 1 megaohm is 1 million ohms = 1 000 000 ohms, so 70 on the 10k setting = 70 x 10k = 700kohm = 700 000 ohms. The multimeter could be a bit off, and/or the pot can be a bit off. You wouldn't want to use such a big value pot, as even with a big resistor hooked up in parralell, the tiniest turn would turn the led off, and forget about being able to control the brightness. You'd want a pot with a max value of about .5k-1k to give good control over an led from say 5-12 volt input, with a series resistor to restrict maximum power to what the led can safely handle. I imagine that some of this sounds a little french, but if you go through the wiki link i posted earlier, and even look up a few more wiki links like you'll find in the article, look up on on leds aswell, then you'll know exactly what's going on. But yeah, you'd be basically doing a mini online electricity course. I guess the summary of it all is that if you had a couple of small value pots and a couple of resistors, which you might have on that guitar amp, you can use the parts to control leds, and you'd only have to buy a couple more parts to control fans. But as i mentioned a better and more accurate way to contol them is to use a diodebus for the leds, and a pwm controller for the fans - you could always use a diodebus for the fans aswell, but there's heaps of options out there. The deciding factors are: How much time you want to spend? Is it a learning experience? Hobby? How much money do you want to spend? Are you just trying to take shortcuts to save a buck or do you want the challenge? If you don't want the challenge then it's not worth the hassle, just buy some controllers.
No burning smell, it looked like it worked except the above mentioned problem with the negligible control.Thanks for letting me know, I'll stop playing with it. btw, thanks for not giving me the finger! Thanks for the confirmation on what my multimeter reading meant. I wonder if it's off. I did get it used. I just found a cool electronics store somewhat nearby, I'll see if they'll test it with me. I'll get some new batteries in it first, and see what I get. What should I see with that pot? 100 x 10k? (I'll try another.) Does megaud = megaohm? What would you say is the ideal pot size for 2 fans of the specs I mentioned before? (depends on the circuit, I imagine. Can I build a circuit utilizing these pots?) And what does the k in .5k-.1k stand for? I've read up a bit on leds and why resistors are needed, and how to determine the needed resistors. I'd like to try to use the same pot, but I saw a few at this store for a few bucks, so I'll get the needed size for whatever circuit I decide on. Yeah, I want the challenge. I wanna be cheap and learn. I do like the idea of this being both an electronics learning experience and a hobby. I do realize this is the more expensive route for the short term (as opposed to buying a readymade solution) so it's a little hard to reconcile with the cheap side with me, but it's fun, and I'll have the accomplishment in front of me. Time is also a concern, and my brain doesn't work as well as it used to when I was younger. I do have a lot to learn, so any recommendations for learning resources would be great. (I know about the stickies and cpemma's site, and also downloaded a bunch of free electronics lessons from somewhere. I forget the exact link (it was recommended source, and i think I got it from some university site, but the material is us navy.) Wikipedia and Google are my friends as well. I have to look into diodebuses still (next), and study up on pwm. I'll probably just be using toggle switches for the leds for now, but I'd really like to use the original knobs for fan control and those weird switches for something (power/reset? Maybe just mount the momentary switches behind them for touch activation, rather than wiring them up?) I'd like to id as much as I can off the board, and test them out for reuse in new circuits, and build a bunch of cool little mods to throw into a bigger mod down the road. I'm taking lotsa baby steps now, and thank you for your bearing with me through this process. btw, the instructions you and the lostmodder provided on logan'srun's project was very helpful to me as well. I've got a decent led control separate from fan power working for the two fans I wanted to do, and I will definitely be using that in the future!
You'd need some heavy duty pots, like wire wound to handle the power of a fan, and those pots aren't that. A megaud is probably just an abbreviation made up by the manufacturer, like a model number or something? And what control options do you wanna go with? Just toggle switches for the leds? I wouldn't want to hook up momentary switches to those big switches on the control panel. It's do-able but a fair bit of work! Unless you found some momentary ones that were the same size! I'd rather use the big switches to control led power, whack in a couple of additional/separate momentary switches for power & reset, and whack in some rotary switches to control fans via a diodebus setup, and a couple of rotary switches for led brightness via resistors. So what type/color, how many leds you want in there? This can greatly affect what types of control & what values of parts you'll need. How many fans, with what power specs? Same thing, affects what parts you'll need.
I just finished reading cpemma's diodebus page, which is great resource, and gives me all kinds of ideas. Up to this point, I really don't know what else I could control besides leds on/off & brightness, ccfl on/off (i believe you can't really dim them because of the inverter, right?) and fan speed. I want to control it all (yeah, control freak.) Since reading about diodebuses, I think it would be cool to have the fans controlled by a rotary switch on a diodebus with led indicators either in a bargraph format or as switch position indicator. I'd like to reuse those funky switches for something (I have 2, but I still don't get what they do.) I'll probably throw in additional momentary switches for power and reset (reuse, recycle!), perhaps stealthed behind the existing knobs, which would not actually control anything by turning, if you get my meaning. I plan on routing the psu switch up to the panel as well, though that may make for accidents when exposed to curious button pushers. I'd like this to be lowkey for the main part, with the ability to transform into a light show, complete with sound activated strobe effects, with a few button pushes and twists. (we all have to have a dream, right?) Of course all this means a lot of new purchases rather than resuse of the existing panel parts. I'll have to look at the board and see what looks useful from it, and what I can id! Everything looks like resistors to me (well, I know capacitors, and there's a few familar looking items, as well as nice labled part numbers of a few things.) I have a hard time making out and matching the bands to the references (slightly colorblind) to figure out the meaning. I'm cool with numbers and shapes, but the colors throw me. I'll throw some pics up, and some guesses, if you (and other bit-techers) wouldn't mind having a go and letting me know what you think. I've got a few different leds (mostly 5mm) from long ago, no specs on em. I also bought a few big green ones from sciplus.com which say 6v, 10M (which I'm assuming is 10mA) . I also picked up a tricolor led (RBG) from linrose which says 1.95/3.5/4.2Vf @20mA. More research on how to hook up the 4 legs is needed as the instructions on the back don't resemble the image shown, or the part number. I'd like to also get some uv leds, if you've got any recommendations, I like blue, green and yellow mainly for coloring.
Well i guess you could have one of those grey switches for led on/off, and the other to swtich between led steady/dance to music mode. I think i've seen cpemma mention controlling ccfl using pwm, but i haven't ever done that and i dunno how much control there would be, if much at all? If you were to stealth a couple of momentary switches behind an unused knob, then i dunno how you would access them? There is actually a way of converting an unused knob into two switches, so that turning the knob one way control's pc power on/off, and turning the knob the other way would trigger reset. It's a bit of work, it might be hard to expain how to mod it, and it wouldn't really be momentary, as you'd have to manually return the knob to center... unless a custom spring mechanism was cooked up, like a centrally mounted coil spring perhaps? Sound activated led's are fairly easy to hook up, just a transistor and a resistor to trigger & power the led's. Reading resistor bands can sometimes be hard, you need to have decent white light to distinguish certain bands on some resistors, moreso with old ones. So if you are gonna put pics up, we can easily be tricked! It would be much more accurate to check them with a cheap digital multimeter, and that way you know they work!
Circuit Check please Ok, I'm going to try a diode bus for one fan right now. I took the plans from cpemma's site, and was hoping someone could check this out and give their input. I'm planning on going to the electronics shop tomorrow and picking up a few things, so it'd be great to get some input before then. All else fails, I'll ask the store owner. So if you're not familiar with his page, here's the link. I've copied his diagrams, and made a few notes with my calculations based on the leds I have on hand. (green, 6v, 15mA). I plan on buying a 2pole, 6way rotary switch as he shows, and the recommended diodes. So here's the first part of the wiring, dropping the voltage for the fan ( I should be able to wire 2 fans up to this, right? I'll start with one, and see what happens.) Diodes 1-6 are 1N4001, rated at 50V, 1A The second part (pole 2 or C): Again, the LEDs I plan on using say they are 6v, 15mA. I got them from sciplus.com (a surplus shop) so I don't know how accurate the labeling is. Diodes 7-12 are schottky IN5817 (Vf of 0.5V or less that can carry 100mA or more) LEDs 1-6 are as mentioned above. Resistors 1-6 I've figured should be 390R. I arrived at this number by using Vs-Vf/Ir = R (12-6)/.015 =400. Hows the Math/Electronics? @mvagusta - I was thinking I could hide the switches kind of like a stealth dvd eject button, just putting it back behind some rod that pokes when the knob or switch is pushed. The 2 switch thing won't work for that, but I might be able to drill out something hold a spring rod behind the knob. Still up in the air about the details of that. I'll look into the sound activation a bit later, right now, I'd be happy to just be able to flip a series on and off. We'll work on automating it later! Thanks for the tip on the resistors, I didn't even think of how I could test them. That sounds great, but I do need to get my multimeter checked out or get a new one. I got a new 9v battery, and it's still showing readings for the potentiometers all over the place. The original one I tested was about 800kohm, while other ones were all over the map (from 200kohm up). They could be bad, or I could have heated them up too much while trying to desolder. I don't know. Right now, I plan on taking a few to the shop and seeing what their meter says.
Circuit Check please part 2 Ok here's where I'm at now: It's based off of the left side of cpemma's schematic. referenced above. I'm using 1N4001 diodes for D1-6 The switch is a 2 pole, 6 position switch. Branded philmore No 30-15206. data sheet is here. I'm not sure of the orientation of the switch. The packaging had a faded mark, and I used the datasheet linked above. From it I could see that A was on the bottom, and figured the other would be C. However which is the bottom? I made some guesses based on turning the stem back all the way counterclockwise, but then realized that it didnt help. There's no indicator.. How can I tell? Also, if you look at pin one at my pic above, I'm not sure that I've wired things properly. See that last lead hanging off pin one? Shouldn't the diode be in front of the pin, not hanging out on its own after it like that? Can I just put the bend in the other side, or should I not? I thought I understand the instructions to mean wire it this way, but I could be off. Lastly, with the 2nd pole of the switch, planning and wiring... I'm doing the bargraph, kinda. I've bought some 1n5818 diodes. They didn't have any 1n5817 as recommended. Will that be a problem? The LEDs I was planning on using are green 6v, 15ma according to the packaging. I figured the resistors to all be the same, at 400, and picked up some 390 resistors. Any tips on the wiring? I was planning on running the wires off the switch to the diode circuit, so I could have a little flexibility in mounting the leds. Any problem with that?
And some more info and pics... btw, are the pics too big? I've wired up all contacts (repositioning diodes at 1-5 to make them come before the position. the reason it was off previously was that I had not properly placed the diode before position4, so I fixed that), connected it and tested it, with mixed results. The leds work great, despite my miscounting the number of resistors to buy, and ending up one short. Leds 1-5 light up in sequence with no problems even without the last resistor/led at position 6. Led 1 stays on and the rest light up as needed. The fan works at positions 3-6, but when I try to turn it down lower than 3, it just goes off (and leds on fan go off at same time). That's gotta be a clue. So what have I got wrong here? I've tried 2 differentfans, just in case one needed exceptionally high voltage to run. I haven't soldered contacts 1-6, pending response from one of the electronics wizs here. I've gone through the wiring of the 1n4001 diodes, making sure the banded side is away from the voltage carrying side and before the contacts. I've got pics galore to show you what's what, and would be happy to take more if neede to clarify how things are set up. Plus, it seems sort of backwards. Highest speed is at position 6, not at position one (I figured on all lit up at position 1 and highest speed, then going down in speed and leds till position 1. Is this how the design is supposed to work, or is it maybe that I've got somethings crosswired? OR could it be because my switch is the "shorting" kind (I think that means make before break, and not the other.) HEre's how the switch is wired: (edit, changed diode orientation for 4-1) Here's the test bed I've got: (bredblox) here it is working at position 5 and here it is not working at position 4 Help!... please.
Sorry, been busy, i just saw this now! So have you got a multimeter? If not get a cheap digital one, and check what voltages are being sent to the fan at each position. This will tell us alot more about what is happening. Inoticed that the diodes weren't mocked up 100% correctly which would have just meant one step had no slow down in speed, but noticed you say that you fixed that up. Another thing to check is hook up the fans straight to 5v, just to see if they will run that low. The only think i don't like is that there alot of bare metal connections that are very close to each other, if i saw your mock-up earlier i would have mentioned using heatshrink or some sort of insulation to prevent shorts.
Hey Mvagusta, what do you mean you have other things to do besides answer noob questions? j/k btw, in case that didn't come through in text! I appreciate your checking in and answering. I took your advice with the multimeter, and checked what was coming to the fan. The readings appeared right from 12-8.5 roughly (old analog multimeter, which I did take with me to the electronics store saturday, and compared a few readings to theirs, but they were busy, and I wasn't as thorough as I would have liked. It appears accurate, though I may get a cheap digital one later, if it seems necessary. off topic, the initial pot I had reads 800kohms, despite the megaud mark, so it's possible that that's how it should be, or its just damaged. Also, all the other pots are different models, and have different resistance to them. That was one of the biggest!) Then, I nudged the mocked up connections (the ends are just held together with small heatshrink (not shrunk) temporarily) and the voltage dropped to 0.... I did some thinking, and a little more purposeful nudging of the diodes, and it came and went again... so I think it's just the loose connection to the position terminal that is causing the drop and the fans to fail. I haven't tried the fans at 5v or 8v, but I'll try it at 5 and see what happens. I'm going to solder the diodes in and see if that doesn't solve the problem as well. I do plan on covering up as much as the bare wire with heatshrink once done. I checked pretty carefully that none of the leads were connecting to anything they shouldn't. I'll let you know, and post final pics if it's working. What do you think about the size of the pics? I believe 800x600 was recommended. I like the detail given, but don't want to cause bandwidth issues for readers or bit-tech... I'm still figuring out photobucket and have my default shrink to at 1024x768. not sure how I can put smaller thumbnails that link to bigger pics on photobucket. EDIT - It works! Finished diode wiring with heatshrink to protect against shorts. Do you think the heatshrink will get too hot around the diodes like that? Showing at lowest speed! So slow some of the pics I took looked like they weren't moving. With 2 fans: Thanks a lot for all your assistance, both planning and followthrough. Thanks also to cpemma for the original plans and answering my pmed questions!
I forgot you had an analog multimeter. It seems fine btw, you don't have to get a digital since you can make do with that. I only mentioned trying the fans at 5v for trouble shooting purposes, but now you know something was either loose or shorting out possibly. Soldering the connections will definitely help if not solve everything, but i'd slip some heatshrink or silicon or rubber tubing over everything as you solder along! If 8.5v runs them slowly enough for you then you probably won't want to reasearch how slow the fans can go, but if you wanna run them more slowly, you can add diodes between each position on the switch to get the voltages you want. Pic sizes are fine for me, and mods probably won't complain as they aren't tooo big, but they might? I usually stick to 800x600 to keep em happy.
Thanks mvagusta, I got it working and edited my last posts with pics (in 800x600, I tend to take a lot of pics while I work.) We must have crossed posts. The guitar amp mod will have to wait to see these controllers however, as I'm gonna put this in one of the other mods I working on (multi-tasking would be a kind way to put it.) I have tomorrow off, so I'm gonna stop by the electronics shop and get parts for another. There doesn't seem to be a problem running 2 led fans off of this, I figure that I would have to check total current drawn by each circuit of 2 fans, led switch, and diode bus to be sure, right? There's no danger of overheating, burning something out is there? I think I should start a separate thread for a problem I'm having with my uv leds, keep your eyes out!
