Noisy solenoid

Discussion in 'Other metal working projects' started by Petee716, Dec 22, 2021.

  1. Petee716

    Petee716 Gold Banner Member

    I’m looking for a little help with a noisy solenoid. This is my control panel. It runs an ancillary latch on one of my production machines which kicks in and out by means of a solenoid. It gets power from the primary machine’s mains which is single phase 208v but the solenoid is 120v, hence the transformer. I assembled the project a few years ago with the help of some of the guys at AA so some of you might remember it, but although it has always worked correctly it buzzes quite annoyingly about one out of every two times it’s activated. It didn’t do it initially but started doing it after about 6 months of use. I can get more photos and give more details if needed. I’m thinking that the SSR has something to do with the trouble but I wanted to toss it out here before I just started changing out components. A936F0EE-2809-4B80-AED3-E1017177C908.jpeg
     
  2. The only electromechanical thing there is the transformer coil, I can't see if you can get a thin plastic or wood wedge between the plastic bobbin and the centre core to stop movement. Also try some rubber furniture feet between the case and the transformer on each mounting bolt to get a compliant rubber mounting.
     
  3. Petee716

    Petee716 Gold Banner Member

    I should have been clearer. It’s the solenoid that’s buzzing (not shown). The noise doesn’t come from inside the control panel. It’s awfully loud. Indications I’ve gotten from reading online point to insufficient voltage. As I mentioned, it only happens about 50% of the time. It happens only when power is initiated to the solenoid as opposed to during operation. If it starts buzzing during initiation it will continue buzzing until the circuit is reopened.
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Is the solenoid being controlled by that SSR?

    Best,
    K
     
  5. Petee716

    Petee716 Gold Banner Member

    Yes. It's hard to see but there is also a resister across the input terminals of the SSR. (If it matters).
     
  6. Smoking Shoe

    Smoking Shoe Silver

    One odd solenoid problem I ran into with my washing machine - an open in the solenoid body that was separated just enough that it would make contact at rest.
    When the solenoid moved during activation the wire also moved and the circuit went open releasing the solenoid. Solenoid closed and contact was again made. Rinse/repeat for a nice house slamming water bang in the pipes.
    The solenoid tested good on the bench - until shaken.
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Could be the solenoid insulation degrading but there's a good chance it's the SSR. There are several methods used for SSRs (probably Triac) and some purpose built for DC vs AC. They're inexpensive and compact but the switching function isn't purely on/off. Read the disadvantages section.

    https://en.wikipedia.org/wiki/Solid-state_relay

    Best,
    Kelly
     
  8. Smoking Shoe

    Smoking Shoe Silver

    If it is safe to manually control the process solenoid (?!?) it should be easy enough to isolate the problem by simply jumpering the SSR output.
     
  9. Petee716

    Petee716 Gold Banner Member

    Do you mean temporarily bypass the SSR?
     
  10. Smoking Shoe

    Smoking Shoe Silver

    Yes. But I hesitate suggesting that without knowing how doing such will effect the down stream process. Safety first!
     
  11. Petee716

    Petee716 Gold Banner Member

    Understood. I gotta respect that.
     
  12. Melterskelter

    Melterskelter Gold Banner Member

    I have heard mention here in the past concerns about disipation of the heat generated by SSR's. Yesterday while browsing SSR's at Mouser's website I came across an interesting factoid:

    Thermal management is a fundamental consideration in the design and use of solidstate relays (SSRs) because of the contact dissipation (typically 1 W per ampere). It is vital to provide sufficient heat sinking, or the life and switching reliability of the SSR will be compromised .
    This was in a datasheet for Accessories for Schneider Electric6000 Series Heat Sink, SSR-HS-1 Thermal Pad, SSR-TP-1 though I would guess it would be similar for other brands of SSR's. One caveat is that the basic design of the relay whether it is Triac or other type.

    The amount of heat generation appears to be directly related to the SSR's "on" time.


    Here is something from Stack Exchange:

    "When the SSR is switched ON, it takes a little bit of power to do the switching, which heats it up a little, but when it's switched ON, the load current has to go through the switch's ON resistance, which causes the bulk of the heating.

    Consider: if the SSR looks like a tenth of an ohm when it's ON and there's 10 amperes going through it, into the load, then the relay will be dissipating:

    P=I2R=10A2×0.1Ω=10 watts"

    I thought the above was helpful as it gives ballpark numbers for the required heat dissipation.

    Denis
     
  13. Melterskelter

    Melterskelter Gold Banner Member

    And just when I thought something as basic as thermal paste/grease should be simple, I started browsing articles about thermal pastes. All the articles agree that thermal pastes lose effectiveness over time. Maybe 2 to 5 years is expected in CPU gaming installations. But then the discussion starts to focus on metal vs ceramic vs diamond etc components.

    I think my take-away is that some thermal paste between the SSR and heat sink is essential (wow, that is earth-shaking:confused:) and maybe it should be replaced after a few years. Is the idea of replacing it periodically worrying about minutia, or is it actually practical. And there it is somewhat unlikely possibility I’ll even think of replacing it in a few years.

    Finally, does anyone have a go-to source for good-quality 20 to 40 amp SSR’s?

    Denis
     
  14. Smoking Shoe

    Smoking Shoe Silver

    Thanks for the tip!
    After a cfew of decades of messing with things electrical - I can still learn something. Could explain why one of my old 'puters just shuts down at random with no observable hot spots or power problems.
    :cool: ................ we need a better suit of emoticons

    Other them buying from one of the name brand suppliers (Mouser, DigiKey etc.) with all of the pirate components in the supply chain getting good quality parts is hit or miss.
     
  15. Melterskelter

    Melterskelter Gold Banner Member

    It’s that hit or miss thing that I really didn’t want to hear. However, it looks like that may be an accurate assessment of the current situation. I don’t mind spending $60 for a decent component as long as it actually is somewhat better than a $15 component of similar description. I recently bought a mechanical relay from Mauser and unfortunately it failed after only five or six uses. That is rather disappointing.

    Denis
     
  16. Melterskelter

    Melterskelter Gold Banner Member

    Knowing no better, I just ordered this unit and some thermal paste. I like the idea of the fan on the heat sink.

    upload_2021-12-24_8-42-11.jpeg

    Denis
     
  17. Smoking Shoe

    Smoking Shoe Silver

    So do I. Wish I'd seen that before I bought what I did........would save some fabrication time.
     
  18. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I don't know how much of rated load Petee is running that relay at but seems like even the steel box should sink heat fairly decent.

    That unit looks pretty nice Denis. Can't go wrong with forced cooling. What voltage is the fan? (Sorry for the jack Petee). When I built my Furnace controller I cast the heat sink. The cabinet is ventilated but the sink is just natural convection. It's pretty massive compared to the relays. With 32 amps though it, it's just barely noticeably warm to the touch.

    http://forums.thehomefoundry.org/index.php?threads/electric-furnace-controller.458/#post-9345

    Best,
    Kelly
     
  19. Petee716

    Petee716 Gold Banner Member

    The SSR is rated for 25amps. Solenoid draws about 41 watts, current @ retracted stroke .35amps (per McMaster Carr) and operates less than 5 seconds on/30 seconds off repetitively. I doubt heat is much of an issue during operation, but I’m here to learn.
    Mi casa su casa.
     
  20. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I'm running the risk of telling you more than I know, but I think operating the SSR at that fractional capacity may aggravate the quality of output signal. Simple way to find out, as the Smoking Shoe suggested, just briefly jumper/close, the SSR during an on cycle, with a pair of probes or external momentary switch, while the solenoid is buzzing. If it buzz goes away, then you know.

    Merry Christmas Petee.

    Best,
    Kelly
     

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