Pulse stretching interface needed

K

Thread Starter

Kurt Holtrop

Are there any commercial products available to convert a 12 volt 50 microsecond pulse into a 24 volt signal stretched out to approx. 1 second
(for input into a PLC).
Thanks,

Kurt

Kurt Holtrop
General Atomics
Bldg 34 Rm 214
PO Box 85608
San Diego, CA 92186-9784

Phone (with Voicemail): (858) 455-3633
Secretary: (858) 455-4198
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E-mail: [email protected]
 
S

Shamsul Kamar Mohamed Jan

Hi Kurt,
For your application, I guess you could check it out with your local Phoenix Contact agent/supplier. I myself use pheonix contact's frequency converter module to extend our machine's length counter pulses from 20ms to
60ms-pulse. To convert your pulse voltage from 12VDC to 24VDC, you probably need an optocoupler which is also available from Phoenix Contact. Below is the part number for Phoenix Contact's frequency converter which could be applicable for your application:

Part No. 2766850
UEGM-OE/AV-24DC/24DC/100
Pulse Width Range: 0/20/50/100/200/500/1000/1500ms

Best Regards,
Shamsul Kamar
Federal Power Sdn. Bhd.
 
K
Try using a SCR. Connect the SCR to the pulse source, the input to the PLC, and an output from the PLC. When the pulse triggers the SCR let the PLC logic drop the output, resetting the SCR. This is a cheap and simple solution. I am sure there are some more costly and complicated methods.

Keith Fargo
[email protected]
 
T

Tanweer Ahmed

You should also take care if the PLC and your DI module(I guess) can process a high frequency input or if you use a 12V high frequency input module or an interrupt module (depending on the brand of PLC you are using) you will probably don't need a converter.

Tanweer Ahmed
Phone: +9221-636 5519
Fax: +9221- 568 2972
E-mail: [email protected]
 
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Rich Anderson

Run the signal into a flip-flop. It will divide the frequency in half. So, 1 flip-flop would take your 50 microsecond signal to 100 microsecond. To go slower, take the output of the flip-flop to the input of another flip-flop, and the signal will then go down to 200 microsecond. Another one, and you are at 400. Keep going until you get the frequency you need.

Changing the voltage can be done with a transistor, or you might be able to bias the flip-flops to provide a 24vdc output.

Rich Anderson
Automation & Controls Programmer
Anamax Group
 
D
OK, but is the object to change (lower) the frequency, or to keep the frequency the same but extend the pulses?

Dave Cooke
 
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Rich Anderson

I thought the request was for a slower frequency (one that could be read by a standard digital input card of a plc as opposed to a high speed counter card) That was why I suggested multiple flip-flops.

If you only need to make the pulses longer, I would still run it into a single flip-flop. The output of the flip-flop would change states with each pulse. So the output would be a square wave. This square wave would be a much longer "pulse" (at 1/2 the frequency)

like this... (best if viewed with a mono-spaced font like "Courier New")

__|__|__|__|__|__|__|__|__|__|__|__|__ <--pulse stream
__ __ __ __ __ __
__| |__| |__| |__| |__| |__| |__ <--flip-flop output

Rich
 
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Vitor Finkel

I would consider an easier approach to trigger a Monostable multivibrator with the 50 microseconds pulse. Calculate the period for the Monostable to be about 1 second. Use the formula ( tau ) = 0,69 R.C = 1 second where R is the base resistor associated with the capacitor C. Beware if a new 50 microseconds pulse arrive almost at the end of the Monostable period occurs, some unpredictable rsults may ocur.

Vitor Finkel [email protected]
P.O. Box 16061 tel (+55) 21 285-5641
22222.970 Rio de Janeiro Brazil fax (+55) 21 205-3339
 
Hi Kurt,
For your application, I guess you could check it out with your local Phoenix Contact agent/supplier. I myself use pheonix contact's frequency converter module to extend our machine's length counter pulses from 20ms to
60ms-pulse. To convert your pulse voltage from 12VDC to 24VDC, you probably need an optocoupler which is also available from Phoenix Contact. Below is the part number for Phoenix Contact's frequency converter which could be applicable for your application:

Part No. 2766850
UEGM-OE/AV-24DC/24DC/100
Pulse Width Range: 0/20/50/100/200/500/1000/1500ms

Best Regards,
Shamsul Kamar
Federal Power Sdn. Bhd.
 
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