1. Home
  2. Electronics Design
  3. Suggestions for Digital Timing Circuit

Suggestions for Digital Timing Circuit

Hi All.

I'd like to build a digital timing circuit and thought I'd see if anyone might be able to offer some suggestions. I'd like to create a timing circuit (all digital, if possible) which can take an input pulse of approx. 500 ms and then, 5-10 seconds later, output a pulse of somewhere between 500 ms - 1 second. Furthermore, I'd like to be able to tweak the delay time, but I don't need a great deal of resolution with the tweaking (if I could have timing increments of 1 second, that would be just fine), and as I said previously, I only need a delay time of 5 - 10 seconds. I know that this type of circuit could be easily constructed using a 555 in association with other circuitry, but I'm curious as to whether or not there might be some type of easier approach using a single IC with which I could perform this relatively simple timing task.

Thanks in advance to anyone who may be able to help!

Reply to
indy465
Loading thread data ...

Use a tiny PIC or a CPLD. Development kits are a reasonable cost and the rest of your twiddling with circuits can be much easier.

Reply to
John_H

Hello indy,

I had a similar question a while back and the thread produced some good info for me although my requirements were a bit different. You can find it here:

formatting link

Good luck!

Reply to
Jimbo

This sounds like a job for CD4000 series logic.

There are a couple of obvious ways to make the circuit.

First version:

(1) Clean up the pulse (so that it goes ground to Vcc etc)

(2) Apply the pulse to the clock input of a CD4013. "D" input of CD4013 is high. This makes a "Delay_in_progress" signal.

(3) Do you have a clock reference? If not make one with a 32768 crystal and an inverter.

(4) Divide your clock reference down to 1Hz in a resetable counter such as CD4060+CD4013. Attach "reset" to the not(Delay_in_progress)

(5) Use the divided clock to clock a CD4017. Reset this also with not(Delay_in_progress)

(6) Wire the last state of the CD4017 to the reset pin of the 1st CD4013

(7) You now have a nice list of outputs on the CD4017 run them to a rotary switch to select the one you want. If you use a 2 deck 12 position switch you can make this the on/off switch too.

(8) Take the selected pulse and use it to drive something like a TIP-35 to make a hard to break output.

(9) Mount it all in a box with a 9V battery holder etc.

Second version:

(1)..(3) as before.

(4) Divide oscillator down to less than 10KHz with method of choice.

(5) Connect two CD4059s to the "10KHz" clock. Connect thumb wheel switches to both.

(6) The first CD4059 is held reset by not(Delay_in_progress) and its output resets the Delay_in_progress flip-flip.

(7) The 2nd section of the CD4013 is clocked by the output of the 1st CD4059. This makes an "Output_in_progress" pulse.

(8) The 2nd CD4059 is held reset by the not(Output_in_progress)

(9) The second CD4059's output resets the 2nd CD4013 section.

(10) buffer the signal as suggested in 1st version and mount in a box.

--
--
kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

Radio Shack sells the 556 dual 555. Use that: an adjustable 5-10 second one-shot followed by a 500ms one-shot. Are you too good for Radio Shack or something?

Reply to
Fred Bloggs

ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.