Pulse to switch

[Dr.EM]

Does anybody know of a way to convert a pulsing signal (eg, square wave, 2v peak to peak) to a switching action (like that of relay). Well, basically, it is a relay I need, but one which can operate at somewhere up to 1mhz, and needs very little energy to energise (ie, from a 555 oscillator). I don't know if its a transistor I want, or FET or something. Any help appreciated!

 

[TheOne]

Generating 1MHz will be a bit much for a 555, which tops off at around 100kHz. One way is to peak-rectify the pulse, smooth to a voltage and detect when a voltage level is present. Another way is with a re-triggerable monostable.

 

[williB]

you could use a FET , but you would have to tweak the signal a bit..

 

[Nigel Goodwin]

Does anybody know of a way to convert a pulsing signal (eg, square wave, 2v peak to peak) to a switching action (like that of relay). Well, basically, it is a relay I need, but one which can operate at somewhere up to 1mhz, and needs very little energy to energise (ie, from a 555 oscillator). I don't know if its a transistor I want, or FET or something. Any help appreciated!

I would suggest you need to give more details, it's too vague for exact replies, but you could simply use a rectifier diode, capacitor, and a switching transistor (plus a resistor or two, and another diode to go across the relay coil).

The value of the capacitor will depend on the frequency of the pulses, and how fast you want the relay to respond.

 

[Dr.EM]

Oops, yeah. Well, it needs to work at around 100k then, possibly less, but much faster than a mechanical relay.

Ok, that suggestion Nigel made, how would I wire that up (schematic)? It sounds ideal.

I don't know what other details I can give, but if it helps, it will only need to switch a 1.5v load. It is currently switched by mechanical contacts, so a device with an output switching that is very close to this is ideal.

 

[Nigel Goodwin]

Oops, yeah. Well, it needs to work at around 100k then, possibly less, but much faster than a mechanical relay.

Ok, that suggestion Nigel made, how would I wire that up (schematic)? It sounds ideal.

I don't know what other details I can give, but if it helps, it will only need to switch a 1.5v load. It is currently switched by mechanical contacts, so a device with an output switching that is very close to this is ideal.

The main details missing are what the pulses are coming from (and perhaps why?), and what it needs to switch - hopefully that information should give us a clue as to what you want to do.

 

[Dr.EM]

Ok, well, this post is related to my other one about the counter circuit. Basically, I think I have found a counter circuit that will cost me pretty well nothing. It comes in the form of a free walkers crisps pedometer, and can count up to 19999. Inside it, there is a little pivot, which touches a contact, and every time it does so, the display advances by 1. I can't really give too many details on how it works, as the circuit is an IC sealed in resin type job. I runs off a 1.5v button cell though.

I will probably have the pulses coming from a 555 oscillator, running at 10-100k. I don't know too much about how much power comes out of one, but i'm pretty sure its a square wave.

So, to make the counter for the speed measure, I need a circuit to convert the oscillator output into switching that the pedometer can count.

 

[Nigel Goodwin]

So, to make the counter for the speed measure, I need a circuit to convert the oscillator output into switching that the pedometer can count.

For a start I would try to test how fast the pedometer will count, I suspect only very slowly - in order to avoid false triggering.

 

[Dr.EM]

Yeah, that was a concern of mine. It responds to a pulse of incredibly short duration, but it may need to wait a while before it can recieve another. So, yeah, I better test that.

 

[hotwaterwizard]

How about a circuit like this?