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| Noob question about resistors for LEDs, but for opto-isolator. |
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| BadMouth:
--- Quote from: DaOld Man on August 17, 2013, 11:53:19 pm ---So you are wanting to switch the resistance to the joystick LEDS, based on an output on or off from the PC? --- End quote --- Yup. --- Quote from: DaOld Man on August 17, 2013, 11:53:19 pm ---How are you switching the opto isolators? --- End quote --- Eventually plan to use a usb Pololu servo controller. It has a mode that can turn LEDs on and off instead of controlling a servo. So far, I'm just using a test bench power supply set to 5v. I might fry a few parts, but I'll get it working soon. It was working for a fairly long time on the breadboard with the 100ohm resistor. It never worked on my proto-board. Maybe it wasn't the low resistance that killed the opto-isolator, but it's not good to exceed specs anyway. I'll go back to the breadboard today and try to find a solution that uses the proper value resistor. |
| BadMouth:
circuit seems to work fine with a 220 Ohm resistor. ::) Hopefully I'll get the same results on the next proto-board. As an aside, I left an opto-isolator on with a 100ohm resistor for a half hour and it didn't burn up. I suspect i fried the one on the original protoboard with the soldering iron or poor routing. |
| DaOld Man:
--- Quote from: BadMouth on August 18, 2013, 01:22:45 pm ---I suspect i fried the one on the original protoboard with the soldering iron or poor routing. --- End quote --- This could well be, but hey, it happens to the best of us, so don't give up. |
| BadMouth:
--- Quote from: DaOld Man on August 23, 2013, 05:29:38 pm --- --- Quote from: BadMouth on August 18, 2013, 01:22:45 pm ---I suspect i fried the one on the original protoboard with the soldering iron or poor routing. --- End quote --- This could well be, but hey, it happens to the best of us, so don't give up. --- End quote --- Pretty sure that's what happened. I barely tacked the next one in and it worked fine. The P1 side of my protoboard worked perfectly, but P2 refused to work no matter what I did. The only difference was that the collector/emitter side of the opto-isolator is reversed. I did that to make power routing to the anodes simpler. I didn't think it made a difference, but apparently it does. Either that or there is some other problem I'm not seeing. I'll reverse them on the breadboard test setup and see if it stops working. Otherwise I haven't really learned anything. ;) At any rate, my protoboard looks like crap from swapping parts, so I'm going to redo one from scratch that I'm not embarrassed to post pictures of. :P I'll use sockets for the opto-isolators and make two identical circuits. Hopefully I'll get it done tonight and will post the final product on my Neo Geo Evolution build thread. |
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