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Post by flateric on Apr 20, 2010 9:17:15 GMT -5
How do I wire up a bi color LED to a dpdt switch to use it as indicator of the switch condition? (This is for a stompbox mini switch). I have a 2-lead bi color LED, basically a red LED and a green LED in the same bulb, one north and one south. So if current flows N->S it glows red, if you reverse polarity it glows green. I need to get this working using the 3 terminals from a DPDT switch
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Post by newey on Apr 20, 2010 10:01:18 GMT -5
OK, so using just one-half of a DPDT on-on? I'm assuming the other pole switches the signal flow? I took a look at this, and I don't see how it could be done with just one pole. It's basically just like wiring a phase switch for a pickup- you need to be able to switch 2 things independently, and you'd need the whole switch to do that. Which, for your purposes, implies the use of a 3PDT, adding in the actual switching of whatever you want the LED(s) to indicate. Now, I've been wrong on this stuff repeatedly around here, so maybe someone else can weigh in with a creative solution . . . and anyone who can do so deserves karma, as it's certainly not going to be an obvious solution.
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Post by flateric on Apr 20, 2010 10:15:03 GMT -5
Aha! Found this on AMZ Musique website: Here is a way to use a 2-pin bicolor LED in a guitar stompbox. The 3PDT footswitch will pull one end of the LED alternately high or low and cause it to change color. When the switch is connected to the top poles, the current flows from the 9v of the switch through the upper LED (green) and through the lower 10k resistor to ground. When the switch is toggled so that the center lug is connected to ground, the current flows from the upper 10k resistor through the bottom LED (red) to the switch and ground. Stomping the switch will alternate the LED between red and green. If you want the red and green to change which switch position activates them, just rotate the LED 180° in the circuit putting the flat side to the right.
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Post by ashcatlt on Apr 20, 2010 11:48:29 GMT -5
You may not have made it from scratch, but I think it deserves a +1 for research. It certainly fits the criteria newey laid out: creative and not exactly obvious!
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Post by flateric on Apr 20, 2010 16:32:01 GMT -5
Thank you sir, I shall be replacing all my boring old LED's with these bi color ones in future builds, more bling !!
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Post by ashcatlt on Apr 20, 2010 17:19:14 GMT -5
You know, that's a pretty good idea for the standard status indicator. It would give a visual reminder to unplug the pedal to avoid draining the battery when not in use.
...Not that I ever use batteries, but I can see where it would be good for some.
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Post by flateric on Apr 20, 2010 17:50:49 GMT -5
I've not yet mastered the art of converting a 9V DC home pedal to Ac without it sounding like a building site full of bees, so if you have any general advice on that side it would be worth a few karma points
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Post by wolf on Apr 20, 2010 18:25:19 GMT -5
I drew my own diagram of that circuit which shows the two "states" of the switch. This is probably a minor concern but it seems the 9 volt battery (if you choose to use one) would always be draining through the two 10K resistors even if you unplugged the LED. Well as I said it is probably minor and I did not mean to rain on your bi color LED parade. (the left is "switch up" for green and the right is "switch down" for red). Since you have a 3PDT switch, I'd guess that you'd want to wire it for true bypass correct? I drew this diagram some time ago and I think it is the way true bypass should be wired. The " standard" diagram just shows the typical SPDT switching wired into about 99% of the stompboxes.
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Post by ashcatlt on Apr 20, 2010 19:24:59 GMT -5
Wasn't it you we helped with power supply filtering a while back? I'll have to hunt up some links, but it really just takes a cap or two across the power supply dumping most wiggles (AC noise) off the DC power. I did it to my Big Muff recently, and don't have any complaints re: noise in the situations where I've used it.
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Post by wolf on Apr 20, 2010 21:53:09 GMT -5
flatericGo to this link at Musician's Friend: Godlyke Power Supply Only orGodlyke Power Supply (and Jumper Cables)The best thing about it is that it doesn't use a transformer which seriously cuts down the hum. If you go to the above link and read the description, it says this can run dozens of effects and has an output of 2,000 milli-amps. Anyway, I own one. It is tremendous - no hum and it can easily powers 6 of my stomp boxes. I imagine you can probably get that from any guitar shop.
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Post by sumgai on Apr 20, 2010 22:19:59 GMT -5
wolf, Sorry, but there is indeed a transformer in there. However, I was surprised to see that Alert box that says "NOTICE: The packaging label is incorrect. It states the device is capable of producing 1700mAH, whereas 2000mAH is the correct figure." Or words to that effect. Hmmmm, I wonder what the folks at UL would have to say about that. Methinks there's a bit of monkeyshenanigans going on here..... However, using this thing to power 6 pedals should be do-able, as most of them suck up no more than 80 to 100 ma., even with an LED or two. HTH sumgai
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Post by wolf on Apr 20, 2010 23:33:11 GMT -5
sumgaiI saw that alert box and it didn't occur to me that anybody can say anything. Sure, just ignore what an official label might say. Our elevator inspection certificate has a misprint - it says it can support 100 pounds - it can actually support 10,000 pounds.
;D As for the Godlyke power supply, their description formerly said it was transformerless (but can still support up to 10,000 pounds). ;D and it previously stated that switching was used to drop the voltage and to change AC to DC. However, if we go here, Switched-Mode Power Supply we will see that article has a section about ... transformer design. LOL
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Post by newey on Apr 20, 2010 23:53:43 GMT -5
Eric-
Yes. Good find!
I, too, have a Godlyke 6-point harness thingy, and it works well, I'm currently powering a variety of pedals with it. If only I'd had the foresight, though, to actually look at my pedal connections before ordering the thing, then I would have known to order more of the various adapter plugs for different manufacturers, to fit what pedals I have.
They give you three of the Boss-type plugs, which are fairly standard, one 9V battery clip adapter, one DOD-style mini phone-plug adapter, and another one which I have no idea what it's supposed to fit (but I don't have one, whatever it is).
So, as yet, I haven't powered 6 effects from it since I lack the correct adapters for several other stompboxes.
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Post by wolf on Apr 21, 2010 0:44:15 GMT -5
Hi newey, So now it seems there are 2 votes for the Godlyke power supply.
I never used the cables that came with it. (At the time I ordered it, I didn't know if it came with the "power supply only" option). I just chopped off all the battery connections on all the boxes and then soldered one length of #18 wire to all the connections. (Hey it works).
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Post by flateric on Apr 21, 2010 1:37:57 GMT -5
I got my mains adaptor plus 5 daisy chains to power a pedalboard from effectspowersupplies, they sell online here in the uk, they work fine with retail pedals but my home made ones really belt out a lot of hum. I'll have to revist the post detailing the caps AC smoothing. No 3pdt in my circuit btw, that was just the diagram i found. To stop power draining all the time the +9v feed for the pcb is fed via stereo jack so when the instrument cable is unplugged the battery is cut off.
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Post by sumgai on Apr 21, 2010 13:26:49 GMT -5
wolf,
As you've noted, I didn't say that a transformless design was not likely, I just said that in the particular instance.... I've got one of those things, and decided (a long time ago) to tear into it, to see what kind of regulation it had.
Quite interesting. What they do is to filter and rectify the incoming AC mains first, then transform that down to where we want it. A zener diode to regulate the maximum output voltage, and Voila!, we're all set.
This design allows for a smaller transformer, which has all the benefits we might imagine, yet still provides a safety margin by isolating the incoming line voltage from the output.
From the standpoint of an Engineering exercise, there are many ways to change the voltage level without a transformer, but in most cases, the safety factor (isolation between the two sides) outweighs nearly everything else.
sumgai
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Post by ashcatlt on Apr 21, 2010 14:24:41 GMT -5
Is there any reason you couldn't just use your existing VRef for this, rather than building a whole new voltage divider?
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Post by flateric on Apr 21, 2010 15:19:53 GMT -5
only that i wouldn't understand how to go about it.. I'll elaborate a little. Its a modded tubescreamer circuit. the circuit is 9v DC battery powered. It has a 3pdt stompswitch. Instead of the single input cap I have leads going off to this dpdt switch with a big and a small cap soldered to it. this is the AMZ fat mod to allow big bass boost at the flick of the switch. Onto the unused poles of this switch I want to put this bicolor led to show what state the switch is in. I can also use this as the main indicator switch to show when its turned on. It would be red or green. If it can be simplified by feeding in the power from somewhere other than the battery terminals via a 2k resistor, then that would be cool.
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Post by JohnH on Apr 21, 2010 15:51:41 GMT -5
The first diagram that you posted looks OK, except that the 10k resistors seem quite high to drive LEDs, and may be dim. Smaller values might be better, but at the expense of more current draw, which is bad if you run off batteries.
In place of the two resistors, I would think that a couple of transistors (arranged a bit like a push-pull output stage on a small amp) could be encouraged to connect the LED either to + or - at the right side, under control of the switch, which would continue to control the left side of the LEDs. So when the switch sends the left side to +, it would also bias on a transistor to connect the right side to -, etc. Only one transistor is on at a time, so there is no wasted current.
Another simplest version however, would be if you could get the two LEDs in a 3 pin package, with both anodes joined, then one resistor and the switch to connect to either cathode would do the job.
John
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Post by sumgai on Apr 22, 2010 3:28:12 GMT -5
The first diagram that you posted looks OK, except that the 10k resistors seem quite high to drive LEDs, and may be dim. Smaller values might be better, but at the expense of more current draw, which is bad if you run off batteries. I agree, it's a bit unusual to see that large a resistance value in an LED supply, but there are "oddball" LED's out there that might need 10KΩ, who knows..... However, what I can say from experience is that in all likelyhood, the two colors will probably have different forward voltages, and thus will require different resistor values, possibly by as much as 25% between 'em. This is often referred to as an "H" control circuit. It does indeed waste current, spent on turning on (and keeping on) the transistor in question - TANSTAFFL. Which makes it overkill. Eric's circuit is fine the way it is, once given the proper resistor values. Presto! (Hint: the image is a link.) There are cheaper ones out there, I just grabbed the first thing Google gave me. And so far as I could determine, all of the 3-lead jobbies are common-cathode, no common-anode devices popped up. Doesn't mean they don't exist, but then again, for wiring purposes, it really doesn't make any difference, eh? HTH sumgai
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Post by sumgai on Apr 22, 2010 3:36:22 GMT -5
........ Onto the unused poles of this switch I want to put this bicolor led to show what state the switch is in. ...... If it can be simplified by feeding in the power from somewhere other than the battery terminals via a 2k resistor, then that would be cool. You say that like it's a bad thing! In fact, the 2KΩ resistor is probably not a good idea - you already have resistors in a chain that work to control the current available to the LED's, so you can most likely drop it. Where your circuit shows "9v", that's what it means - hook up the battery (through the main power switch, be it a toggle or one of the TRS jacks), and you're good to go. Not much way to make it any simpler, or any more reliable! HTH sumgai
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Post by flateric on Apr 22, 2010 7:03:47 GMT -5
For most stompbox LED indicators I put a 2k resistor in, I'll try that for these bi color ones, also bought meself a pack of the three-legged LEDs from ebay so I'll try them out on the next build - wiring will be a little simpler
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Post by ashcatlt on Apr 24, 2010 12:49:32 GMT -5
Is there any reason you couldn't just use your existing V Ref for this, rather than building a whole new voltage divider? None of the folks here gave us an answer on this one, but I caught flateric double-posting over at DIY Stompboxes and got this response to the same question: "You can't just use an existing Vref because the LED will mess with the voltage. When the LED is connected to ground by the switch it will pull the divider voltage down to what ever the forward voltage of the LED is, when it's connected to +9 it will pull the voltage up. It would probably work if you put a resistor between the LED and the divider, but you still might pull more current than the divider can provide which again will mess with the Vref voltage. Probably a risk of pops as well caused by sudden changes in current."
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Post by JohnH on Apr 24, 2010 15:21:05 GMT -5
Leading on from that, it helps to reduce my concern about wasted current passing through the resistor voltage divider. Because the voltage at the centre of the voltage divider is pulled up and down depending which LED is on, the current that is flowing without going usefully throuh the 'on' LED is only the LED forward voltage (maybe 1.5-2V) divided by the resistor value, rather than half the supply voltage / R.
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Post by sumgai on Apr 24, 2010 20:52:12 GMT -5
John, Actually, the current flow through the "on" resistor will be the same as that flowing through the LED itself - check with Kirchhoff's Laws for the proof of that one. ~!~!~!~!~ ash, I'm not so sure that the DIY stompboxer has it correct. A simple analysis shows that current flows through one resistor and one LED, period. It never matters whether that series-connected pair are hooked directly to V ref, or through some other resistor, the end result will be the same - the overall resistance must be calculated to yield the correct amperage through the LED, or else said LED will be either too dim, or blown all to smithereens. Now, if the voltage divider is too low an overall value, then there's a real risk of acting like a short circuit to the power supply. That's more than just messing with it, that's downright asking for trouble. But short of that design failure, a voltage divider directly across the power supply is done so often in electronic circuitry that it's not even funny. I won't call "Bojer" on this person, but I have to say that I do smell a rat behind the wallboards..... HTH sumgai
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Post by flateric on Apr 26, 2010 16:08:24 GMT -5
You caught me ash. I have both types of LED's now but still debugging the circuit which is unusual as I've put together quite a few TS pcb's nowe and they normally work straight out the bag. When i correct the problem I'll finish the extension switch and LED wiring.
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Post by flateric on Apr 29, 2010 16:46:03 GMT -5
Here's the finished article, debugged, bicolor LED works a treat, added a 9v dc jack socket. Well pleased with this, the phat switch brings in a higher value cap to let thru a big slab of bass. The clip switch brings in one of 2 different sets of antiparallel diodes, either normal si type or a couple of little LED's. The sound difference is vast! great versatile pedal for lead or bass, covers all the grounds from cruch thru fuzz to overdrive
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Post by newey on Apr 29, 2010 20:38:20 GMT -5
That looks like a sweet project, Eric! Any chance you could post a schematic? Did you build this on perf or etch a board? I've been thinking maybe we need an effects schematic sub-board hung up- maybe this should be the first entrant there.
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Post by flateric on Apr 30, 2010 7:08:17 GMT -5
Can't take credit for the circuit, its modded from the standard TS808 layout found in Aaron nelson's DIYStompox site. Here's a post from me in the basschat forum explaining the mods: basschat.co.uk/index.php?s=&showtopic=74856&view=findpost&p=742574This is built on home-etched pcb, although I used a little square of perfboard to mount a few different pairs of clipping diodes then wired that to a rotary switch.
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