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VB.NET Program to send Voltage signal in milliseconds

I am currently needing to write a VB.NET program that will do the following:
-- I need it to send a 4mA signal at 80 milliseconds
-- I need it to send a 20 mA signal at 180 milliseconds

I would like to do this in VB.NET as it is language I am most familiar with, which isn't saying a whole lot :).

I am thinking if it is possible to just send the different voltage amounts out the USB port, which has up to 500mA of power?

I hope that is enough information. I am just seeking the best way to do this, it doesn't have to be USB or a program, but just need a way to send those two signal voltages at that speed.

Thank you for you help and thoughts!!

David Johnson, CD

what about multiples of 4 * 9 send out 24mA ?? (every 36 cycles) and for how long is this pulse?
my thinking is that you need a simple circuit with current limiting resistors to limit the current.. USB doesn't have fluctuating current it just supplies a voltage with a MAXIMUM current of 500mA. So you need to have 2 ports that you can toggle on and off and then use an op-amp or transistor that once voltage is applied to its base will allow current to flow.

sscottinandrews

ASKER

Sorry most of that makes sense; however, I wasn't quite clear. I have a device that has a position of top and of bottom. It is controlled by a laser. The laser in order to know where top is to send it a signal of 20mA within 180 ms, then position it at bottom and send it a 4mA signal at 80ms. So it is set device at top send signal, set device at bottom and send signal.

So going out each port into a capacitor makes sense, just how? Or is what I just described still doable?

Thank you!!!

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David Johnson, CD

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sscottinandrews

ASKER

I actually believe the best approach to be Arduino board as I can program it to send the signals I need by tracking the state of the button. Thank you ve3ofa for your comments, and yes I didn't actually mean a capacitor earlier as it would certainly not do what I want. As for ohm's law, I am pretty sure I memorized that in Physics years ago in college, but I am pretty sure I can get away with not needing it for this project. Although it would make a lot easier.

Again, I do appreciate the advice, I technically only wanted to know how t write the VB.NET code to do the sending of the signals, the "trivial part".

Thanks again!