Post Created date
AVR controlled rocket, needs failsafe mode
Danni and JayHay put their finger on a critical problem. I wouldn't depend totally upon active firmware safety. If somehow the controller gets a reset and doesn't properly detect...
Wednesday, 29 August 2007 - 00:38
Reset caused by induced interference?
Trigger on the relay drive and observe transients on or near the AC mains peaks. Correlate that with what you see on the VDD pins. While reviewing this thread, I thought that you...
Wednesday, 15 August 2007 - 17:01
Diode in VCC line.
If you are going to put in a diode, why not an SOT23 LDO at 3.3V? You get a predictable supply voltage and the logic levels should match well enough. The output filter cap is the...
Tuesday, 14 August 2007 - 17:17
Reset caused by induced interference?
Lots of good suggestions for hardening your board to the tranients comming off the AC load. I would suggest C0G for the 1nF caps instead of X7R, you get better bandwidth. As noted...
Tuesday, 14 August 2007 - 01:43
ATMEGA8L bandgap voltage reference
A simple way to get around the initial Vbg value problem is to set up your ICP hardware to measure the reference and then either tell the DUT to save that value as a calibration...
Saturday, 30 June 2007 - 00:32
AVR Dragon goes "POP"
Hmm. I would avoid powering all but minimal target loads with the Dragon. And, if you are frying your Dragon, be prepared to see that again. Switching regulators have a negative...
Wednesday, 20 June 2007 - 18:26
Land Line Modem Details
BTW, for the old voice band 300 to 2400 baud modems, the answering modem does not put carrier on line immediately on answering. It puts out "Answer Tone". When the originating...
Wednesday, 20 June 2007 - 18:07
serial resistors on LED output pins: are they needed?
The basic question is one of risk versus benefit. How careful do you need to be, what is the downside of failure, are the guards against alpha particle and programming errors...
Saturday, 24 March 2007 - 03:36
serial resistors on LED output pins: are they needed?
It's all a question of peak and average limits. If the peak is too long in duration, you will get the controller too hot. If you drive too hard, even averaging won't save the chip...
Saturday, 24 March 2007 - 00:15
serial resistors on LED output pins: are they needed?
Keep in mind when designing with LEDs that their forward voltage characteristic is NOT controlled for. Small differences in knee point can make for interesting differences in...
Friday, 23 March 2007 - 20:59
serial resistors on LED output pins: are they needed?
LEDs typically are capable of handling some very short, intense pulses. Think 1% duty and very fast rep rates.
Friday, 23 March 2007 - 19:35
serial resistors on LED output pins: are they needed?
I would expect the controller to give up sooner than the LED. The latter is a bit more rugged, though you can kill them. Typically, if you get an LED hot, the clear plastic melts...
Friday, 23 March 2007 - 18:30

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