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KJD series switches.

Discussion in 'General Electronics Discussion' started by boyd, Nov 6, 2016.

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  1. boyd


    Oct 7, 2016
    I have posted a couple of times before with this project. Attached is a very simple circuit of how I plan to control my 2.2kw dust extractors with just turning on the machine. There is a whole lot more I am going to add into the system.

    I found the cheapest way was to buy US$1.70 230vac to 12vdc power supplies and install them into each machine. This will give me a 12vdc output once a machine is switched on.

    What I have done though is use a single solid state relay to switch on the extractors whereas the KJD series of switches are double pole with built-in under current/voltage protection. I will be adding in those along with a couple of other sensors.

    If anyone was interested, I would really be interested in feedback as to whether this will be fine to go or I need to have double pole relays to switch the extractors on and off or can I just do it with the phase hooked up to the relay on a single wire to on/off?

    Also I am looking at a way to cheaply put in a 30 second delay before the extractor switches off along with the current/voltage protection. I have found these to put in the low voltage side:

    Now I just need to find current/voltage protection.

    But I am VERY keen to hear from anyone more qualified than I if I have missed something?

    Regards Boyd

    Attached Files:

  2. dorke


    Jun 20, 2015
    I would say that for safety reason alone you should
    use a double pole relay to switch both Phase and Neutral.

    Could you please explain the need for this arrangement?

    Notice that the "12V P.S." will "indicate" a working M1 machine,
    while M1 may not work at all due to a malfunction in M1.

    What kind of machine is M1?
  3. Bluejets


    Oct 5, 2014
    Maybe I read it wrong but wondering how you expect a time delay to operate after the power shuts down to your power supply units.
  4. boyd


    Oct 7, 2016

    It is a joinery workshop. So M1 is a typical machine of about 8 machines. If M1-8 fail to start and I get a 12vdc signal several things will happen.

    1: My extractor starts - or continues to run if I have just changed machines within the set time delay.
    2: A pneumatic solenoid will operate through an additional control system to physically open a gate in the 100mm dust extraction piping.

    If machine one does not operate yet I get 12VDC I will immediately know and be resolving the issue with M1-8.

    I have decided to install two solid state relays in each extractor cuircut for neutral and phase. They are cheap. I am also putting in a time(off) delay on the low voltage side, and current/voltage protection in the high voltage side (I might just put in a breaker) Funny, I well know 230VAC can kill but the last job I was on I ended up troubleshooting 3KV lol

    As for the time(off) delay I plan to insert two of these:

    Into the 12vDC side of the extractor control.

    I am going to use four of these:

    Thoughts? See problems?

    Obviously I am earthing EVERYTHING! Along with a fire security system.
  5. Bluejets


    Oct 5, 2014
    If M1-8 fail to start and I get a 12vdc signal several things will happen.

    This can never happen.( as drawn)
  6. boyd


    Oct 7, 2016
    Ok. I smoked my relays! I don't know if its because they are cheap or if 40A is too small for a 230v 2.2KW motor.

    First - one of my single phase motors uses a KJD17 (I think) to start. I was unsure how to wire it so just connected the cap and motor (four wires coming out of the motor) in parallel. The SSR exploded and blew a breaker. Wow. Good smoke. Must work out how to wire it???

    I connected the other 2.2KW motor in a basic circuit shown in my drawing. The SSR operated once but then fused closed circuit when I removed the 12vdc input. So the motor keeps running and has done with all 3 relays I had spare. Except for one relay which has a resistance of 3k ohms when I input 12vdc.

    There is a whole bunch of other stuff in the operation but what has stumped me is why the relays are fusing closed circuit. Too much initial current draw from the motor?

    I do plan to install SSRs on the phase and neutral but my initial attempt at getting this running has failed at what I expected to be the easy part :-(

    Can anybody please tell me I am wrong in what I have done? And what I should do?

    This is the relay

    Uploaded is the basic wiring.

    Attached Files:

  7. boyd


    Oct 7, 2016
    Hey so might be talking to myself now because you guys think I am a wolly. Anyway I have bought a bunch of 80A relays.

    The ones I bought, latched the first time and then stayed latched!

    Except for one. Picture attached. I have wired a single phase motor 230v. This on a single capacitor. Four wires coming out of the motor so I connected them in parallel. Basic terms, the cap and motor winding in parallel as I though was supposed to be.

    The picture attached was the result. Direct short!! Now I have looked on the net and am a little confused. I wonder if the KJD 17 switch that has the "extra" terminal is momentary contact only and that there is no centrifugal switch in the motor?

    I know I must be sounding like a novice dork but gee. So I cut one of the cap wires. The motor starts, but slower than the other machine I have. Although the other identical machine (extractor) is a two cap motor.

    Anyway. Smoke and Bang is always interesting. So here tis a pic. I am looking forward to installing the 80A relays but would still like to get to the bottom of the motor issue.

    I have also attached a picture if anyone is interested of the pneumatic control gate I have designed and cut out with my home built cnc. It works!

    Attached Files:

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