24VDC Flip flops?

[python01]

Does anyone know if 24VDC j-k flipflops are availbable anywhere? Would like to do divider working with 24vDC signals and using 24VDC supply

 

[dknguyen]

Sounds like you may be going about accomplishing your end task incorrectly. WHat are you trying to do?

 

[python01]

I am getting pulses which I need to feed into plc but the pulse length is to short so I would like to divide them to make them longer. I don't care about the length of the pulse when it goes into plc input, just need to know if the pulses are happening at all.
That is why it would be convenient to connect 24VDC devices.

 

[Reloadron]

Sounds like you are looking to buils a missing pulse detector or a retriggerable one shot multivibrator. Have you given any thought to building the circuit (your flip flop) using transistors? Note the monostable flip flop (one shot) on this page. It uses 2N3904 transistors but could use any commom NPN like a 2N2222. With some minor parts alteration it would run on 24 volts just fine. Would something like that work for you?

Ron

 

[crutschow]

If you are going into a PIC, why do you need 24V? Just use a resistive divider to reduce the signal to a normal 3.3V or 5V logic level and then stretch the pulses from there using normal IC logic circuits

 

[python01]

I am sure the circuit would work but I am looking for divide by 16 or maybe even 32 which would make this circuit huge, using flip flops would be easier and much smaller. If I could get them in 32VDC version I would not need the voltage regulator and relay to get it back to 24VDC.
I am connecting to PLC input, not pic.

 

[crutschow]

Sorry, I misread the word plc.

So, if you want to stay with 24V, then you need to do it with discrete transistors that can tolerate the voltage. Divide by 32 would require a minimum of 5 flip-flops or 10 transistors and associated resistors, diodes, etc. such as this **broken link removed**.

 

[Reloadron]

I am getting pulses which I need to feed into plc but the pulse length is to short so I would like to divide them to make them longer. I don't care about the length of the pulse when it goes into plc input, just need to know if the pulses are happening at all.
That is why it would be convenient to connect 24VDC devices.

I am missing something in this. When you refer to the "pulse length" are you referring to the PW (Pulse Width) or the PRT (Pulse Repetition Time) as in the frequency?

My read is that you have a pulse train fed into a PLC. Thus the 24 volt logic. You want to know if the pulses stop? I assume that is what you mean by "need to know if the pulses are happening at all".

Thus I suggested building a re triggerable one shot multivibrator using two transistors. You set an RC time constant that exceeds the PRT. If the pulse train is interrupted the output will change logic states. As long as pulses keep coming along in a pulse train the out state will not change. Thus I also used the term 'missing pulse detector".

If for example my PLC is monitoring a rotary encoder on a motor shaft and I want to know if the motor stops I would run the pulse train from the encoder into a re triggerable one shot.

Ron

 

[python01]

Reloadron,
Could you point me to circuit diagram on the web?

 

[Reloadron]

This would work better if we knew exactly what your application is? For example if you have a 24 volt pulse train from a sensor there may be ways to interface the pulses to something like a 74HC123 then take the output from the 74HC123 and have it drive a simple transistor to get you back to 24 volt logic levels. This all ties into exactly what you have. For example a Google of "re triggerable one shot" would get you started. If there is an easy way to condition the signal you have to what you need for a chip and then back to what you need for a PLC input that may be the easy way to go about this.

Ron

 

[python01]

I have 24VDC pulse train, frequency of 1750Hz. It comes from proxy sensor detecting rotation of motor shaft. The pulse width is very short and my PLC input does not detect it. I would like to stay with the 24VDC if possible to avoid signal conditioning but will look at other options if it is not possible.