Problem understanding HCF4541 Programmable Timer Datasheet

[bigal_scorpio]

Hi to all,

I am trying to build a long interval timer using the HCF4541 IC and am not getting the results I expected, but I am not certain that I am reading the datasheet correctly.

This is how I am using the IC.

Pin 1. (RTC) 100k
Pin 2. (CT) 50pF
Pin 3. (RS) 200k
Pin 4. Not Connected
Pin 5. (Auto Reset) to Gnd
Pin 6. (Manual start) Touch to +5v to start timer
Pin 7. Gnd
Pin 8. (Output) to LED through 1k
Pin 9. (Output low or high) to +5v
Pin 10. (Single transition mode) to Gnd
Pin 11. Not Connected
Pin 12. (Frequency Select A) to +5v for 256
Pin 13. (Frequency Select B) to Gnd for 256
Pin 14. (Supply) to +5v

If I put the manual reset line to +5 and power up I get a pos on the output.
If I put the manual reset line to Gnd and power up I get a neg on the output.
If I remove the connection to M/R then the output gives an alternating signal.

I was expecting nothing on the output ( except maybe momentarily),until I had started the count and it had completed.

The datasheet is puzzling me to say the least. Can anyone suggest where I am going wrong?

I think I am reading the logic and timing tables correctly and that the 200k, 100k and 50 pic is all in range? What is my problem here?

Thanks, Al

 

[audioguru]

Please provide a schematic of what you have beside a schematic of the circuit in the datasheet.
Then you will see what is wired wrong.

 

[bigal_scorpio]

Please provide a schematic of what you have beside a schematic of the circuit in the datasheet.
Then you will see what is wired wrong.

Hi Audioguru,

I have drawn out my circuit and I still don't see what the problem is.

Maybe I am getting confused with the datasheets meanings but I am stuck at the moment. Give me a clue.

Al

 

[dr pepper]

Your reset input pin 6 is shown not connected to anything, it will float in this situation causing random resets due to noise.

Try a 2k2 or thereabouts resistor from pin 6 to ground, and then connect your pushbutton to +v.

 

[bigal_scorpio]

Hi dr pepper,

I see what you mean mate but just tried and still same results.

Al

 

[audioguru]

The timer is working normally.
1) It is set for Auto Reset during power up.
2) If the input pin 6 is low then it times for about 3 seconds after power up. If pin 6 is high then the timer is always reset.
3) Pin 9 sets the output high after reset then the output goes low after time-out.