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Author Topic: SSR relay wont power down  (Read 1756 times)

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SSR relay wont power down
« on: February 23, 2017, 10:31:26 AM »
Im doing a retrofit on an older  sharnoa a cnc  machine. I have Dmm Ac servos ess board w/ c62 bob. Im trying to hook my coolant ssr relay up . I can power the pump fine but when I go to shut it down it stays running. The input and load are connected properly . The input is the 4.95v from the ess the load is 220v.
Any suggestions?

Offline Davek0974

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Re: SSR relay wont power down
« Reply #1 on: February 23, 2017, 10:40:36 AM »
If you disconnect the input, the pump stays running??


If yes then the SSR is blown - permanently on is a favourite failure mode for SSR's.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.
Re: SSR relay wont power down
« Reply #2 on: February 23, 2017, 12:49:03 PM »
This is a common problem with many manufactures. A quick google search will show that . Once the load triggers the on mechanism/ circut they wont shut off until there is a certain lack of or provided volts. People use different resistors or capacitors to achieve this . Im not savy enough to know.
I have ten new solid state relays . I doubt there all bad.
could be though

https://www.google.com/webhp?sourceid=chrome-instant&rlz=1C1HLDY_enUS731US732&ion=1&espv=2&ie=UTF-8#q=ssr+wont+turn+off
« Last Edit: February 23, 2017, 01:01:44 PM by mrich0908 »

Offline Davek0974

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Re: SSR relay wont power down
« Reply #3 on: February 23, 2017, 01:58:01 PM »
Sounds like you might need a pulldown resistor to ensure the output from the board goes below the threshold voltage of the SSR.

I'm not sure of values here but a 1k resistor between the SSR input and 0v would not do any harm, can't guarantee it will work though :)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.

Offline Tweakie.CNC

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Re: SSR relay wont power down
« Reply #4 on: February 24, 2017, 04:36:33 AM »
Probably does not apply in this case but...

There are various types of SSR's with the most common type designed to switch the load ON / OFF at the zero crossing point of the a.c. mains waveform - they will not operate correctly with a d.c. load.

Tweakie.
KEEP SAFE !

Offline Davek0974

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Re: SSR relay wont power down
« Reply #5 on: February 24, 2017, 04:59:34 AM »
Yes, i read this as an AC 220v pump.

Sounds like the BOB output is not dropping low enough to release the SSR.

OP - can you get your SSR turned on then confirm it WILL stop the pump if the 5v signal is disconnected at the SSR?
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.
Re: SSR relay wont power down
« Reply #6 on: February 25, 2017, 09:39:18 AM »
As I wrote Im doing a retro fit. One of the older power supply for the 24v AC had a ceramic capacitor the bridges the two -+ sides together . I hooked that power supply up with that capacitor  and boom it works.
I have no clue what capacitor it is because the top of the resistor is laminated in a red wax material .
At least im on the right track.

Offline Davek0974

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Re: SSR relay wont power down
« Reply #7 on: February 25, 2017, 12:24:23 PM »
If it is a red round type of component it's probably a MOV or metal oxide varistor - a type of self resetting shunt that helps prevent voltage spikes.

Glad its moving on :)
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives.
Plasma table, Mach3 V062, Step motors, C&CNC THC.