Re: IR emitter circuit design

by cyborg5 on Sun Feb 24, 2013 5:01 pm

Sea Moss wrote: It's certainly not surprising that it bonks out when presented with a load like this. Current is really limited here by the ability of the source to deliver it. For a battery that depends on its internal resistance…


If I operated the Arduino Uno or Leonardo off of a battery such as a USB recharger battery (commercial version of a minty boost) can I pull the 5 V off of the Arduino +5V pin or doing I need to somehow power the circuit completely separately from the Arduino? Like I said in earlier post I think a single LED with a single NPN is going to be good enough for this application but if I'm going to chalk this whole thing up to a learning experience I want to learn all I can.

My problem was that I had built a single LED single NPN circuit that works pretty well but when I built a second one I had problems with it. I think the first one had a wide-angle LED which was working pretty well for me because my distances were not too great. The one that wasn't working very well was narrow angle which of course meant that the position was critical. I was thinking I wasn't getting enough power when in fact I was getting too much accuracy of direction. I'm going to rebuild another one with a wide-angle and see what happens. I just didn't get a chance to do it today.
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Re: IR emitter circuit design

by Sea Moss on Sat Mar 02, 2013 6:42 am

I think you can expect to see the Arduino cutting out if the Arduino and the LEDs are both running off a USB port or a garden-variety voltage regulator as found on the Arduino board. No idea if your proposed USB charger has a current limit, or whether it might be high enough. I do know that you can run four IRLEDs in this configuration off a phone-type lithium battery and not get dropouts. One way to get a semi-isolated supply for the MCU that protects it from the biggest voltage excursions is to feed it from the common 5V supply through a diode, with electrolytic caps to ground on either side of the diode. Also if you are using 5V and your battery can supply the juice, you might find that you start burning out IRLEDs. The TVbG is a crude but sneaky design that does away with any real current limiting because we know that the planned power source can't supply enough current to damage the LEDs.
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Re: IR emitter circuit design

by cyborg5 on Sat Mar 02, 2013 11:54 am

I tried it with one USB charger and it would not power the Arduino when the adrenal wasn't doing anything special. The client draw was so low that the charger assumed the battery it was charging was charged and so it shut itself :-(

I tried a different one and it seems to be working okay with two LEDs. Also use a 1A USB power supply and it appears to work okay. So the only problem I have is powering it off of a regular PC USB port.

I realize TV-B-Gone is the proverbial "brick $#!+ house" in that it is overengineered. I think I'm going to have good success with two LEDs for my particular project. I let the battery working okay and my only problem is testing the code while plugged into the PC. I think I may try sticking a 9 V supply in the barrel jack to supplement while plugged into the PC.

This is been a great learning experience for me. I've got the whole thing laid out in Eagle CAD and once I do some more double checking will be submitting to BatchPCB or some other similar service.
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