Easy pulse generator

[electronicbasickid]

Hi,

I am trying to make a short pulse generator from any pulse input. By this I mean I want a final output with a fixed pulse width no matter what input I have.
I tried to do it with a not gate linked to a and gate. It did work but apparently the solution can be based on ONE component only.

Any ideas?

Thank you in advance.

 

[DPG]

Hi,

I am trying to make a short pulse generator from any pulse input. By this I mean I want a final output with a fixed pulse width no matter what input I have.
I tried to do it with a not gate linked to a and gate. It did work but apparently the solution can be based on ONE component only.

Any ideas?

Thank you in advance.

The good old 555 timer IC connected as a monostable would make a good job of this.

I can't see how it could be done with one component though.

 

[Lucien Nunes]

The good old 555 timer IC

Fixed that for you. The 7555 is a better IC that does not stomp all over the Vcc at every output transition.

There are lots of monostable options, you can build your own with transistors or use an IC. The main consideration is whether it should be re-triggerable, i.e. what it is supposed to do if another input pulse occurs part-way through an output pulse; does it start timing again, or does it ignore the second pulse to ensure that the output pulse is of standard length?

Some circuits have pathologies that can be important to know about depending on application and pulse width. For example, you can get misshapen output pulses if the input pulse is just barely long enough to trigger. IIRC the once-popular 'LS121 suffers from this one. Also the quality of timing capacitor can be critical especially for long pulses (in which case a counter is usually better).

 

[marconi]

10.5 Edge-triggered Latches: Flip-Flops - https://www.technocrazed.com/10-5-edge-triggered-latches-flip-flops

Further to previous advice:

If what is attached does not make sense to you then come back. To provide some points of interest and topics to research an electronics engineer would have the following questions:

1. What is the specification of the input pulse you which to detect and then stretch for a pre-determined period. ie: Is it a standard two-state logic signal or some other two state signal? How noisy is it? Is there a minimum time period of the input pulse which has to be exceeded before a stretched pulse is output? What is the nature of the input pulse - periodic or random? What frequency?
2. Do you want to trigger the stretched pulse when the input pulse transitions low to high - leading edge - or when it transitions high to low - trailing edge?
3. Is the circuit one-shot and then inhibit? ie once a trigger occurs and there is one output pulse and then no further input pulse transitions will cause a further stretched output pulse until a reset signal is applied?
4. Further to 3 above - Is the circuit one-shot and then timed inhibit?
5. Do you want a controlled reset during the period of the stretched pulse being high?
6. Is the logic circuitry part of combinational or sequential logic circuitry? Is the logic circuitry Synchronous/Clocked?
7. When power is first applied what do you want the output state to be?

Anyway - by way of practical help and with simplicity (always a good thing) in mind - I have two 74LS122 retriggerable one shot and clear ics gathering dust in my shed. You can have them free if you want. Send me a private message with your address and I will put them in the post. The deal is that if you do use them you report back your success with pictures. I will add in some 555s too.

https://www.ti.com/lit/ds/symlink/sn74ls122.pdf?ts=1636101701394&ref_url=https%3A%2F%2Fwww.ti.com%2Fproduct%2FSN74LS122

 

[DPG]

Looks like the OP hasn't been back since Tuesday when he asked the question. Let's hope he returns.