PicMaster Posted December 28, 2010 Report Posted December 28, 2010 Has anybody made this very old project work properly?It will probably work properly if it is built according to the datasheet for the IC.I brought a kit from Velleman which was based om the ICL7107 and I found that this gave unstable readings and could never cure the bouncing of the readings, May be this is why they stopped selling it ?So in the end I decided to design and build my own based on the MAX7219 and PIC16F876, This gives accurate and stable readings and is now used in my Velleman PSU 0-30V 0-10A, I used ISIS to simulate it to get everything working(Picture attached) and then designed and built the PCB for it.I like the idea of LED'S because where my PSU sits at the back of the bench I don't have to lean forward to see the LCD version. Plus I use the green version which is better Quote
mendimano Posted December 29, 2010 Report Posted December 29, 2010 There are two versions of the old ICL7107 IC. The newer version ICL7107S has improved Stability.The LED display draws up to 224mA through the IC which heats it a lot and causes it to drift.It needs an additional -5V supply but you don't say how you produced it.The L7805 regulator must have the two small capacitors shown on its datasheet. It needs a minimum input of +7V so the average rectified and filtered voltage must be more, depending on how much ripple is produced by the filter capacitor. If the rectifier is full-wave then a 1000uF filter capacitor reduces the ripple to 1V peak. The transformer should be 8VAC or more at 500mA. Im using the the ICL7107 CLP version,i have produce the -5 volt with IC ICL7660 Quote
mendimano Posted December 29, 2010 Report Posted December 29, 2010 I brought a kit from Velleman which was based om the ICL7107 and I found that this gave unstable readings and could never cure the bouncing of the readings, May be this is why they stopped selling it ?So in the end I decided to design and build my own based on the MAX7219 and PIC16F876, This gives accurate and stable readings and is now used in my Velleman PSU 0-30V 0-10A, I used ISIS to simulate it to get everything working(Picture attached) and then designed and built the PCB for it.I like the idea of LED'S because where my PSU sits at the back of the bench I don't have to lean forward to see the LCD version. Plus I use the green version which is betterhi Picmaster is it posible from you to post the schematic and pcb of this volmeter of yours? ( PIC based) Quote
gogo2520 Posted December 29, 2010 Report Posted December 29, 2010 I built one over a year ago and it worked good as long as 1% resistors were used, there were two projects posted at the time so I don't know which one you are referring to.gogo Quote
mendimano Posted December 30, 2010 Report Posted December 30, 2010 gogo im refering to this project Quote
gogo2520 Posted December 31, 2010 Report Posted December 31, 2010 Hello mendimano Yep that looks like the one. I had to use 1% resistor onR1, R2 & R3. and the voltage divider took a little playing around with. It worked, still have it hanging on the wall.have fun gogo Quote
mendimano Posted January 1, 2011 Report Posted January 1, 2011 Thanks for your tips gogo, seems reasonable to use 1% resistors for more accuracy,ill try that and i hope it will work beater then, and happy new year Quote
gogo2520 Posted January 3, 2011 Report Posted January 3, 2011 I found when I was doing some web searching, maybe it will yougogoICL7107_tips.pdf Quote
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