Monitor power supply voltage on SCADA - PLCS.net

Engineer1 · July 7th, 2006, 08:29 AM

Hi All,

Thanks for the great help... here I go again...

I need to monitor the power supply voltage going into sliprings, basically from a 24v power supply. But I want to monitor this via a momentum PLC. Basically something similar to a multimeter with outputs. Only I just need the voltage only.

Basically the system suffers power dips now and again. When the slip rings (copper based) are getting dirty, I just need to monitor when the supply voltage begins to drop indicating that the slip rings are getting dirty and then get them cleaned.

Help will be greatly appreciated. I tried looking around this site for a similar problem, but it looks like I am out of luck.

Thanks,

jtn · July 7th, 2006, 08:49 AM

I have seen battery voltage in remote panel SCADA systems monitored by using a voltage divider (2 resistors) sized so that 24V would be ~5V into an analog card. A voltage input should have a high enough impedance that it's current draw can be neglected in the votage divider equation, but you can check to be sure by looking at the specs for the card.

George Graziano · July 7th, 2006, 08:50 AM

If your looking for a specific value of voltage, say 22.2V, then get a converter that can take your 0-25V and turn it into your analog input. If your looking for if it drops below 19.9V I have used voltage relays, that I set the drop out voltage and it becomes a digital input to the PLC.
George

Mickey · July 7th, 2006, 08:58 AM

Have a look here: Model SIX
http://www.miinet.com/products/sg_signal.shtml

tomalbright · July 7th, 2006, 12:17 PM

I used a 1500 ohm resistor on an analog input to get 0-30 volts.
scaled 0-20 ma.

Engineer1 · July 19th, 2006, 11:38 AM

thanks guys... had a look around and found that a transducer could do what i am asking for. but for the price, it is not worth it.

what i am simply needing now is a contact that will go on when a voltage larger that 24V DC passes through, and go off when the voltage drops below 20V DC, this can be a digital input signal to my momentun PLC.

a fancy proximity switch if you ask me.Is there a product like this out there? cheaper than a transducer off course.

CharlesM · July 19th, 2006, 12:09 PM

Take a 24v relay and put a 10K pot on the + side. Turn the pot down till the relay drops out then up till it comes on.

Just an idea.

jtn · July 19th, 2006, 12:19 PM

http://www.automatictiming.com/pdf_div/vba_data.pdf

Is this what you are looking for?

Engineer1 · July 20th, 2006, 04:23 AM

this is it... thanks a lot!

July 7th, 2006, 08:29 AM	#1
Engineer1 Member Join Date: Jan 2005 Location: In a decent flat Posts: 24	Monitor power supply voltage on SCADA Hi All, Thanks for the great help... here I go again... I need to monitor the power supply voltage going into sliprings, basically from a 24v power supply. But I want to monitor this via a momentum PLC. Basically something similar to a multimeter with outputs. Only I just need the voltage only. Basically the system suffers power dips now and again. When the slip rings (copper based) are getting dirty, I just need to monitor when the supply voltage begins to drop indicating that the slip rings are getting dirty and then get them cleaned. Help will be greatly appreciated. I tried looking around this site for a similar problem, but it looks like I am out of luck. Thanks,

July 7th, 2006, 08:58 AM	#4
Mickey Lifetime Supporting Member Join Date: May 2003 Location: Palmdale,Ca Posts: 7,591	Have a look here: Model SIX http://www.miinet.com/products/sg_signal.shtml __________________ Mickey If you want happiness for an hour-take a nap. If you want happiness for a day-go fishing. If you want happiness for a month-getmarried. If you want happiness for a year-inherit a fortune. If you want happiness for a lifetime-help someone else. ----- Chinese Proverb

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July 7th, 2006, 08:49 AM	#2
jtn Member Join Date: Jan 2006 Location: Washington Posts: 235	I have seen battery voltage in remote panel SCADA systems monitored by using a voltage divider (2 resistors) sized so that 24V would be ~5V into an analog card. A voltage input should have a high enough impedance that it's current draw can be neglected in the votage divider equation, but you can check to be sure by looking at the specs for the card.

July 7th, 2006, 08:50 AM	#3
George Graziano Lifetime Supporting Member Join Date: Jul 2004 Location: NY Posts: 328	If your looking for a specific value of voltage, say 22.2V, then get a converter that can take your 0-25V and turn it into your analog input. If your looking for if it drops below 19.9V I have used voltage relays, that I set the drop out voltage and it becomes a digital input to the PLC. George

July 7th, 2006, 12:17 PM	#5
tomalbright Member Join Date: May 2006 Location: Gonzales, LA Posts: 676	I used a 1500 ohm resistor on an analog input to get 0-30 volts. scaled 0-20 ma.

July 19th, 2006, 11:38 AM	#6
Engineer1 Member Join Date: Jan 2005 Location: In a decent flat Posts: 24	thanks guys... had a look around and found that a transducer could do what i am asking for. but for the price, it is not worth it. what i am simply needing now is a contact that will go on when a voltage larger that 24V DC passes through, and go off when the voltage drops below 20V DC, this can be a digital input signal to my momentun PLC. a fancy proximity switch if you ask me.Is there a product like this out there? cheaper than a transducer off course.

July 19th, 2006, 12:09 PM	#7
CharlesM Member Join Date: Aug 2005 Location: Arkansas Posts: 1,085	Take a 24v relay and put a 10K pot on the + side. Turn the pot down till the relay drops out then up till it comes on. Just an idea.

July 19th, 2006, 12:19 PM	#8
jtn Member Join Date: Jan 2006 Location: Washington Posts: 235	http://www.automatictiming.com/pdf_div/vba_data.pdf Is this what you are looking for?

July 20th, 2006, 04:23 AM	#9
Engineer1 Member Join Date: Jan 2005 Location: In a decent flat Posts: 24	this is it... thanks a lot!

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