Understanding Solid State Relays controlling 120 vac Vibrators

[robertmee]

With the diode, only the upper or lower half wave conducts and that can alter the proper functioning of the SSR.

You could try connecting a resistive load in parallel with a diode + vibrator, for example a tin soldering iron or an incandescent bulb of about 100W. Maybe then it will work

Also try reversing the cables at the SSR output terminals.


If it were in parallel something would have burned, at least the fuse.

Yeah, my bad....was thinking a back EMF diode on a DC circuit.

 

[joseph_e2]

Do you know that the diode is for sure good? Even under load? If it fails short, the vibrator won't have the rectified power feed it's expecting and if it fails open, then nothing happens.

 

[tripstuf2]

SSR operation:
Typically control half is 4-32VDC, there are also AC versions of control.
When 24VDC is applied to control,(make sure polarity is correct), it causes the "latch" of the controlled output. Simply put it is an electronic switch. If you verify 24vdc at control, then output should have close to 0 ohms, or if under power, both sides of output to ground should show the same voltage. If only the input side of output has voltage, SSR is bad.
In my experience, 99% of time they fault closed, like on all the time, but have had failures to open.

 

[strantor]

In my experience, 99% of time they fault closed, like on all the time, but have had failures to open.

I also experience more failures closed than open but not 99%. For me more like 60-70%, but still I think it is highly improbable that 8 out of 8 failed open, statistically speaking.

 

[Baker in Virginia]

Thanks for all your help . Tomorrow I may use a 24 VDC power supply and mimic the analog output . Strange thing is , none of the vibrators are working , from the solid state relays . I will try the 24 VDC power supply on the input of the solid state relay . I read 24 VDC on the inputs of all the solid state relays from the analog outputs . If it is analog , I’m just wondering why they didn’t just use 24 VDC digital outputs .

Thanks again ,

 

[parky]

I don't believe these relays should use an analog to drive them according to the datasheet it should be a DC voltage the "B" type is instant on switching i.e. as soon as it sees a voltage on the input it should trigger. Are they trying to control the vibrator speed ? if so I don't think the SSR is the type

 

[strantor]

I don't believe these relays should use an analog to drive them according to the datasheet it should be a DC voltage the "B" type is instant on switching i.e. as soon as it sees a voltage on the input it should trigger. Are they trying to control the vibrator speed ? if so I don't think the SSR is the type

Ordinary SSR can be used with an analog signal if something like this is implemented. Nothing like it was mentioned but the analog signal doesn't make sense otherwise.

 

[parky]

That was just my point, it is possible that bubba has replaced what was originally 4-20ma or 0-10v controlled SSR's with what they assumed would work, not unusual seen things like this before where some in-experienced engineer has substuted with something they thought would work, it depends on if the original drawings show the same part number as are installed now or not.
@ Baker: Do you know if this may be the case, also you mention 24v at the analog card yes but although the standard voltage supply will be 24v it would normally be either 0-10v or (0) 4-20ma signal I cannot see where if they are current output cards that varying the current would make a difference in the control of the ssr as they seem to be digital switching not variable.

 

[Baker in Virginia]

Good Morning, Yes , that is what I’m thinking . I’m new here and just walked into this issue . Yes, I can see that a few Solid State Relays were changed out . I normally build my own stuff . It was a company called CSS International that built this .

Thanks

 

[padees]

Good Evening ,

I should know more about Solid State Relays . I have
a system with 8) 120 vac Vibrators . These Solid State
Relays have a 4-32 VDC Input . The analog input is reading
24 vdc , but none of these Vibrators will work .

To begin with , what really does the 4-32 VDC mean ? Any
voltage 4 to 32 volt will trigger the Solid State Relay ? There are
Diodes on the wires going out to the Vibrators . I took the wires
off the Solid State Relays , and placed the wires on a 120 VAC terminal
and all 8 Vibrators run. Depending on the 4-32 VDC output from the output
of the PLC , does that determine how much of the 120 vac , pass through to
the Vibrator ? Thanks so much for your help .

I'm not sure I want to field your questions, but you have some good answers on how SSR's work.


Let's look at the vibrators.


Your description assumes that an SSR with 4-32VDC input will alter the 120VAC output to the vibrators.


I may be wrong, but the vibrators you may be using are just choke coils, not unlike a choke coil that pulls in a relay, just that they are mounted on springs with an air gap.


They operate at 60Hz, and if you increase the voltage, it increases the magnetism/intensity. As long as they don't slap, and get stuck, you have a vibrator.


Is there a variable transformer, or similar device down stream of the SSR?


An SSR would not be my 1st choice (not even on the list) In dealing with this.


Maybe someone confused SSR with SCR? I have no clue?