AC to DC Interface Relay with filter.

Hi guys. I have a 120vac signal coming from a microswitch triggered by a cam. I am trying to interface this signal to a high speed counter card which takes 24vdc as it's inputs.

Does anyone know where I can get an ac input to dc output that would also filter out the microswitch bounce. Maybe an interface with a rectifier and rc circuit or something like that.

Thanks.

Can you replace the micro switch with a 24v dc proximity ?

The answer may depend on the cycle time. If it is very fast, several times a second, you should follow LD's suggestion.

If the cycle is slow enough to use a conventional relay it will be self de bouncing, since there is a minimum pull in time for the relay coil.

If the cycle time is intermediate you need a solid state relay. You can use a debouncing timer on the input, where an internal coil isn't tripped until the input is on for a preset time. You then use the coil's contacts instead of the actual input in your logice. Some PLCs actually have an adjustable debounce in the card configuration too.

Thanks for the replies guys.

I cannot change the microswitch or the voltage of the microswitch as it is 100 ft. in the air in a standalone unit.It also still needs to interface to the original controller.

I decided to use a high speed counter instead of running it into a standard 120vac input because I did not know the exact frequency of the pulses and feared it might be faster than the scan time.

Tom, I am using a DL-06 with a high speed counter in the expansion slot. I don't have filters for the inputs and I am afraid that by using a solid state relay I may also get the switch bounce pulses. I may have to experiment with one though.

Ok, I ordered a CC1150-ND Solid State Relay from Digi-Key. It takes AC or DC input and outputs DC. I will let you guys know if it works for me.

you can provide a 120 v AC interfacing relay in your input signal and connect the contact output of the relay witn 24 V DC to your circuit. However there will be small time delay dependining on the interfacing selected.

The contact output would actually increase the count by 30-40 in the high speed counter card because of the contact bounce. I believe it will require a solid state device.

I assume 60 Hertz. Full wave rectification will give 120 pulses per second. That means 120 dead spots. How 'high speed' is this signal? A cam and microswitch tells me that this signal is fairly slow. Was the 120 vac originally planned for a mechanical counter?
If this is a slow signal, I doubt that a high speed input is necessary. It should be slow enough to use Tom's suggestions.

The original 120vac microswitch signal went into a proprietary display, so apparently they are handling the signal interface on their display board.

I think the maximum microswitch rate is about 10 hertz. This should work with a standard 120vac input since the scan time is well below 100ms.

I guess at this point I am just wondering if it could be interfaced with a HSC in case I run into a similar situation in the future with a faster switching frequency.