Edge-trigger circuit

[ex.digital]

Hi

My name is Martin, and I am not very experienced with electronics. I know what the different components do in theory (transistors, capacitors, resistors, diodes, ...), but going from that and designing a circuit is a big leap for me. This is why I am here. I am trying to design a circuit (not homework, just hobby), which has to do the following:

I have a TTL, which can deliver +5V or 0V, depending on what instructions I give it from a computer. When the circuit gets +5V, the circuit should be able to deliver a pulse (the precise length is not an issue, it just has to be a pulse) capable of driving a coil. This coil should e.g. move a magnet/shutter of some sort. When the circuit gets 0V, it should deliver a similar pulse to another coil -- i.e., the shutter/magnet now has to move the other way. The magnetic is very small, just as the coils.

So this is faily simple in theory. Here is my analysis so far: The circuit must have to different output channels, and a single input channel. Furthermore it must be connected to a power supply, which can drive the coils. I thought that I could use some sort of capacitor to make the pulses, but I am not sure how this works in practice.

I would be very happy to recieve some feedback.

Best wishes,
Martin.

 

[barry]

Hi Martin,

What you are looking for is two edge-triggered monostables. Look at a CD4098 (TI and others make this). This is a very old device, but I think it's still available and will do exactly what you want. It has two monostables (which is a device that will produce a pulse every time it sees a trigger edge). The nice thing about the CD4098 is that is has TWO monostables in one package, and you can configure them to trigger on the rising or falling edge. You'll probably need some transistor or mosfet on the output to drive your coils.

good luck!

 

[ex.digital]

Hi Martin,

What you are looking for is two edge-triggered monostables. Look at a CD4098 (TI and others make this). This is a very old device, but I think it's still available and will do exactly what you want. It has two monostables (which is a device that will produce a pulse every time it sees a trigger edge). The nice thing about the CD4098 is that is has TWO monostables in one package, and you can configure them to trigger on the rising or falling edge. You'll probably need some transistor or mosfet on the output to drive your coils.

good luck!

Hi barry

Thanks for that, I will check it out. I have just finished talking to a fellow student of mine (who is actually an engineer), and he told me that he had made a circuit similar to mine with TL084CN.

 

[barry]

Well, a TL084 is an opamp. It will take a lot of extra components to turn that opamp into 2 monostables. :--)