telephoneman Posted January 25, 2007 Report Share Posted January 25, 2007 is there a chip out there to drive 7 -10 leds that will count pulses from a 555 and hold the lights on until the last pulse and restart? working on a project for school and having trouble finding the right chip to make the project do what my instructor is asking for. tried a 3915 with a capacitor to make the same effect but he would like to see if i can find something drive by a 555. PLEASE HELP. Quote Link to comment Share on other sites More sharing options...
AN920 Posted January 25, 2007 Report Share Posted January 25, 2007 I don't know about a single chip apart from a micro. Discrete it could be done with a row of D-type flip-flops wired as serial-in-serial-out (SISO) shift register and clocked by the 555. You may also use 2X 8bit shift register chips with the proper feedback after 10 stages. Quote Link to comment Share on other sites More sharing options...
Fowkc Posted January 25, 2007 Report Share Posted January 25, 2007 Sounds similar to a project I did for GCSE. I had the 555 clock a 4017 decade counter. Each output was connected to a thyristor that turned an LED on. Thus after 10 pulses, all the LEDs were on. It's not the ideal solution, because it requires 10 discrete thyristors, but it worked. Quote Link to comment Share on other sites More sharing options...
AN920 Posted January 25, 2007 Report Share Posted January 25, 2007 Also there will be a problem to turn off the scr's when the count restarts. Quote Link to comment Share on other sites More sharing options...
Fowkc Posted January 25, 2007 Report Share Posted January 25, 2007 Hmmm... can't remember how I got round that... perhaps it wasn't an issue, not sure - it was a good few years ago!But there must be a way around that problem. The last 4017 output could be used to turn on a PNP transistor to switch the SCR power on. When that output goes high, the transistors turn off and the SCRs reset. Again, it's not elegant (you only get 9 outputs), but it probably works. Quote Link to comment Share on other sites More sharing options...
telephoneman Posted January 26, 2007 Author Report Share Posted January 26, 2007 thanks for all the help so far... i'll see if i can get something going.. if anyone has anymore ideas... i'd love to hear them.... THANK AGAIN. Quote Link to comment Share on other sites More sharing options...
AN920 Posted January 26, 2007 Report Share Posted January 26, 2007 You can do it many ways, some less elegant than others. Quote Link to comment Share on other sites More sharing options...
aries1470 Posted February 4, 2007 Report Share Posted February 4, 2007 is there a chip out there to drive 7 -10 leds that will count pulses from a 555 and hold the lights on until the last pulse and restart? working on a project for school and having trouble finding the right chip to make the project do what my instructor is asking for. tried a 3915 with a capacitor to make the same effect but he would like to see if i can find something drive by a 555. PLEASE HELP.Hmm... why not use a simple decade counter? and instead of using an LED, re-route the output to keep the appropriate led's on in order from 0-9?Here is a simple circuit here, but just try to think on how to 'convert' it... ;-)http://www.aaroncake.net/circuits/counter.htmI will leave that part up to you :-D it is a very simple circuit and ready to take a pulse from a 555 timer too. just remember to keep your voltages within limits. Quote Link to comment Share on other sites More sharing options...
ante Posted February 4, 2007 Report Share Posted February 4, 2007 You might be able to use the UAA180. Quote Link to comment Share on other sites More sharing options...
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