abador Posted March 13, 2011 Report Share Posted March 13, 2011 I was trying to use LTSpice to design a circuit and it showed a spike at the transistor which was way above the power rating that I needed to accomplish. I added resistors at the base and the collector to try and limit this spike and ran another simulation of the wattage at the transistor and there was still a spike of several watts. Is this something to be concerned about or could it be a glitch in the program? Is there something I can do to prevent this?I just looked at the simulation again on the aspect of the current and noticed that the current is a simple square wave and it dips down into the negatives every so often. The voltage is normal from what I an see. Is this a common glitch with LTSpice? Quote Link to comment Share on other sites More sharing options...
Hero999 Posted March 13, 2011 Report Share Posted March 13, 2011 To allow one 555 to control another you're better off just connecting the output to pin 4, rather than switching the eintire power supply.Don't worry about the power spike, it's unavoidable and is caused by the fact the transistor can't turn on/off instantaneously. It's not a problem because it lasts for such a short length of time it won't overheat the transistor, even if it exceeds its maximum rating. Quote Link to comment Share on other sites More sharing options...
abador Posted March 13, 2011 Author Report Share Posted March 13, 2011 Is there any way to get the circuit to delay without the transistor? In the simulation I noticed that it would turn the LED on for a certain amount of time then the circuit would turn off when the chip timed out which is the opposite effect that I wanted. Quote Link to comment Share on other sites More sharing options...
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