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Looking at a data book I find that the 8 pin parts only work with an AC input. Connect the input signal through a capacitor, .1uF should be OK, and connect a resistor from pin 1 to ground, 10K or so. It won't hurt to put another .1 uF cap from pin 6 to pin 8 as well. The 2917 part is supposed to be connected to 9V through a 220 ohm resistor. After you get the 2907 working, try the '17 with this resistor as there is a fair chance it survived your assault on it.
Thanks!
When you type connect the input through a capacitor do you mean in parallel? I connected the .1uF capactor in series to the freq input at pin one and then ~11K resistors (didn't have a 10K) in the same breadboard row from pin one to ground. I also tried 222ohm at the 9 volt positive side in series to the positive bar and added another .1uF between 6 and 8. I tried the circuit with both the 2907 and the 2917 and neither worked... I bumped the frequency up to 494 hz and it still would not light the LED.
Is there a simpler circuit I can setup to test these chips?
What is this data book you are referring to? I would never have come up with these suggestions- thanks!
When you type connect the input through a capacitor do you mean in parallel? I connected the .1uF capactor in series to the freq input at pin one and then ~11K resistors (didn't have a 10K) in the same breadboard row from pin one to ground. I also tried 222ohm at the 9 volt positive side in series to the positive bar and added another .1uF between 6 and 8. I tried the circuit with both the 2907 and the 2917 and neither worked... I bumped the frequency up to 494 hz and it still would not light the LED.
Is there a simpler circuit I can setup to test these chips?
What is this data book you are referring to? I would never have come up with these suggestions- thanks!
The input cap is in series , one side goes to the frequency source and the other to pin 1. The 220 ohm part is series with the battery . Connect one end to the positive bus, plus 9V, and the other end to pin 6. The two 5K resistors are connected pin 6 to p7 and p7 to p8. Your frequency setting parts may be wrong. My formulas are R1C1=1/2f. And C2=50C1.
The book I got in 1980 so it's not available. The information should be found on the web, just enter LM2917 into google.
A simple way to test parts is to make an Osc with a 555 or Schmitt trigger IC.
The book I got in 1980 so it's not available. The information should be found on the web, just enter LM2917 into google.
A simple way to test parts is to make an Osc with a 555 or Schmitt trigger IC.
Looking back at your pics I can see that your timing parts are wrong. R1 should be 50K. C1 ,to pin2 would be .1 uF for 100 Hz, 1.0 uF for 10 Hz. The 10 uF cap connects to pin 3 (+) and Gnd (-). After you make these changes please post some more pics, hopefully with the LED lit.
Okay EinarA you are a genius! Thank you everyone for your help!
IT WORKED!!!!!!!!
Both the LM2917 and LM2907 worked with the corrected timing parts!
The .1uF capacitor in series with the input is absolutely essential! What does it do? The pull down/pull up resistor (11K at pin one to ground)- I am sure helps but is not required- is this to force the logic state?. Same with the .1uF capacitor from pins 6 to 8- not required but likely helpful? What is this capacitor designed to do? Interestingly, the LED flickers without the 222 ohm resistors in series with the positive 9 volts at the same frequency...
The circuit threshold is stable at 10.85 Hz. It flashes from 10.2 to 10.85.
I do not understand why a 47K resistor (I didn't have a 50), and flipping the capacitors worked though as the answer is the same 10 Hz with the 5K resistor and 10uF capacitor?
Is it because C2 must be larger than C1 with that other formula you got from that book? We are only at 10C1 so would 50C1 be more stable?
Thank you! Thank you! Thank you!
IT WORKED!!!!!!!!
Both the LM2917 and LM2907 worked with the corrected timing parts!
The .1uF capacitor in series with the input is absolutely essential! What does it do? The pull down/pull up resistor (11K at pin one to ground)- I am sure helps but is not required- is this to force the logic state?. Same with the .1uF capacitor from pins 6 to 8- not required but likely helpful? What is this capacitor designed to do? Interestingly, the LED flickers without the 222 ohm resistors in series with the positive 9 volts at the same frequency...
The circuit threshold is stable at 10.85 Hz. It flashes from 10.2 to 10.85.
I do not understand why a 47K resistor (I didn't have a 50), and flipping the capacitors worked though as the answer is the same 10 Hz with the 5K resistor and 10uF capacitor?
Is it because C2 must be larger than C1 with that other formula you got from that book? We are only at 10C1 so would 50C1 be more stable?
Thank you! Thank you! Thank you!
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I'm happy you succeeded. The cap at the input is needed because the input must swing plus then minus to trip the charge pump, your input only goes from Gnd to V+. A 47K resistor is needed at p3 because the charge pump only puts out 200 uA and the the voltage at p3 must go above 1/2 V+; so R1 must be greater than V+/200uA which I rounded off to 50K. The LED flickers as you move through the threshold because the voltage at p3 is not steady, it moves up when the pump puts out current, then falls back. Making C2 bigger will make this ripple voltage smaller but to completely stop the flicker you connect a large value resistor from p5 to p7. This makes the output jump past the ripple voltage point. Try 470K. The cap from p6 to p8 is a bypass cap, it helps steady the voltage at the IC. I hope you remembered to put in the 220 ohm resistor when you plugged in the 2917 as it isn't meant to run on 9V. The LED in this case still goes to 9V. I see from the pic that you have the resistor in series with the battery for both versions. This is OK but change the connection for the LED so it powers directly from the battery so it doesn't load down V+ when it is on.
Einar, could you share the ISBN or author/title of this databook? Maybe I could find an old version on Amazon ? The secret is probably more likely your translation as that Texas Instruments data sheet might as well have been in a foreign language as I couldn't pull anything useful out if it...
Does the capacitor pull it below zero when it draws to refill combined with the pull down effect of the resistors? I didn't have a resistor as big as a 470k so I used one 240k and was going to add another in series but the 240 alone eliminated the ripple as far as my eye can tell...
I fixed the LED, thanks!
Does the capacitor pull it below zero when it draws to refill combined with the pull down effect of the resistors? I didn't have a resistor as big as a 470k so I used one 240k and was going to add another in series but the 240 alone eliminated the ripple as far as my eye can tell...
I fixed the LED, thanks!
? I searched a lot and never find a good one !- Status
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