Recent content by circuitmangler

First of all I'd like to thank everyone who responded to my earlier question about adding ESD protection - it all was very helpful information. My new question is this: suppose we have a USB-powered microcontroller based device, and some of the uC pins are exposed as an external I/O port (i.e...

CarbonWorks - thanks for the lead. I'll look into it.

IRStuff - in my case the encoder is a simple led/phototransistor and is powered by the decoder device.

I have a device that was manufactured in the early 90's that uses LS7166 quadrature decoder chips. The AB inputs of the LS7166s were connected directly to external rotary encoders using DIN connectors. After many years of use and repeated plugging and unplugging of the DIN connectors almost all...

jimkirk - that's a good idea and I'll be sure to check that out. itsmoked - I thought I gave it the ol' touch test to see if it was overheating, but I can easily check that again.

Hi, I have a used Elenco Digital/Analog trainer, and on board there is an adjustable 0-20 VDC power supply. However, ever since I've had it it's only been able to adjust from 0 to 10 V. I've just gotten around to looking at it, and figured out the following: - It seems like a standard LM317...

Here are some forums you can check out: yahoo group Electronics_101 yahoo group Homebrew_PCBs http://dutchforce.com/ http://www.electro-tech-online.com/ http://www.electronics-lab.com/forum/index.php

jimkirk, geekee - thanks for the feedback!

Hi, I have a device which operates off of a 9V battery, and I'm investigating removing the need for a power switch as follows: the device has an earphone jack, and so I was thinking of using the shunt lead of the jack (which is grounded when no plug is inserted and is an open circuit otherwise)...

Hi guys, The point is not to save money but just to gain a better insight into how you could build one yourself. Thanks for the tips -- cm

melone -- the purpose of the these hand-held devices is simply to provide a convenient way to see what leds look like under different current loads. they have multiple testing circuits so you can place them side-by-side for comparison. So, they could be used for a variety of purposes, i.e...

benta - thanks for pointing that out. I looked for limits on supply current, but couldn't find it on the first datasheet I found. Now that I have looked at some others, I see where the supply current limits are explicitly stated. thanks again!

itsmoked... yes, the voltage regulator approach is simple, but the op amp approach is only $0.09/circuit. The lm317 can supply higher currents, though, and would be useful for testing LEDs at > 50ma. Having multiple testing circuits available is nice for doing side-by-side comparisons of LEDs...

I think I just realized that one op amp can't be used to test multiple currents -- at least the circuit shown won't work that way. oh well... back to the drawing board. cm

Hi everyone! I'm sure most people are familiar with the hand-held LED tester boxes that have come out on the market recently, e.g. the ones that look like this: http://www.ledtronics.com/ds/TST-1001/ For a while now I've contemplated how easy it could be to make one yourself with an emphasis...