hi, i designed a counter with jk ffs. it count from 0 to 9 and resets at 10 to 0...
ffs get their clock pulses from circuit i designed with a LDR, aim of this, is to increase the counter by 1 when LDR s light goes off( when i put my hand on ldr, i should see that 7 segment increase by 1)
but when i energize the circuit, i see 0 at 7seg, and when i put a light towards ldr, 7seg becomes 1, but when i put off the light it goes back to 0 again...
This is most likely due to the input of the 7400 nand gate (U4 lower pin) being pulled high permanently instead of being wired to pin 11 of U2B. Or you could have a faulty U2. Check to see if you get the correct logic (should be 0 on powerup) on input of the 7400 and pin 11 of U2.
Hi spidey99,
I would say, forget the LDR-transistor part and give such slower generator signal (i.e. KHz..) as clk for your circuit & test it with a scope...
K.
Sorry, Im not involved with counters/digitals...
Your "hand effect" isnt only a "controlling through hum"?
Do you have such bypassing 100nFs on your ICs?...
K.
I'm not sure, but try these:
1. Do not float the SET pins. Tie them to Vcc.
2. Try to use a monostable in between the transistor output and input to FF.You may be getting too many pulses at the output of transistor.
3. Use a low pass filter with the LDR. Simply connect a 1uF capacitor across R4.
thanks matbob,
-what do you mean with monostable? do you think a schmitth trigger work that way?
-should i connect the capacitor in series with r4 or parallel?
Connect the capacitor parallel to R4. Just search in GOOGLE what is a monostable and its purpose.Schmitt trigger is different and cannot be used in place of a monostable.