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Thread: an Electrical switching question

  1. #1
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    an Electrical switching question

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I have been working on a machine and wanted to fit a low voltage pilot light to the machine as the low voltage ones seem to have more options of size and shape. I wanted to swap out the existing dim button light for a 12V LED strip light as it would fit with the new look of the machine.
    The problem i have is switching. Currently the pilot light comes straight off the element terminals so when the element is on the light is on. If I am to change the light to one of a different voltage I would need to have an electronic switch to switch the low voltage light on and off. In my experience (limited) I have only ever seen a SSR that uses a low voltage to switch a higher voltage. Is there one that works the other way?
    I don't have a lot of room to instal a dedicated 12v transformer for this light, the brew controls are currently 12V so i already have a 12v supply i just need to be able to control it.
    Im sure there are people with a lot more electronics experience who can point me in the right direction

  2. #2
    Not a Shoe Jimmytheboot's Avatar
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    There are SSRs to do what you want, look at rs online and filter by control voltage and load voltage.

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    cheers, Its just knowing the terminology to put into the search.

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    Mal Dimal's Avatar
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    G'day Aaron...

    An SSR is not necessary or even the best way to go for this type of load. Personally, I'd be using one of many decent quality and inexpensive electromechanical relays for this. You'd never wear it out before the machine needed major remedial work...

    Be careful working around 240V AC though, it is now illegal in most Australian States to attempt this without the necessary qualifications and license.

    Mal.
    P.S.
    There is a simple way to this electronically too but given the need to interface with 240V AC circuitry, it really should only be attempted by an appropriately licensed person.
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    Thanks Mal,
    I am very careful doing this kind of work - both low voltage and 240V. I share workshop space with an electrician who has helped rig up my workspace with appropriate earthing and GFCI switched power. I also have him check my work where ever possible before i throw the switch.
    My biggest problem is while my sparky mate knows how to wire up a house, when i start talking to him about relays he is not much help sourcing an appropriate sized components - everything he deals in is as big as a pack of cigarettes or bigger.

  6. #6
    Mal Dimal's Avatar
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    G'day Aaron...

    Suitable relays and mounts can be obtained online from several reputable retailers like the one pictured below from Ocean Controls. I'd suggest the unit below to be ideally suitable for what you have in mind...

    240Vac-10A Relay.JPG 240Vac-10A Relay Base.JPG

    Mal.

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    thanks Mal
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    You wouldnt even need a relay if you simply used a tiny switching power supply. Just supply it across the element and run the xlv directly to the led strip.

  9. #9
    Mal Dimal's Avatar
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    Quote Originally Posted by koshari View Post
    You wouldnt even need a relay if you simply used a tiny switching power supply. Just supply it across the element and run the xlv directly to the led strip.
    What would the cost of small SMPSU be compared to a simple relay?
    You would still need to factor in a small regulator and dropping resistor on a small PCB (ideally) to avoid the LED fluctuating in brightness due to any load variations.

    Mal.

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    Bugger all for the load that led strip will draw. And you will need a supply with the relay anyway.

  11. #11
    Mal Dimal's Avatar
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    Even tiny SMPSUs that I've seen cost more than a relay/base/wall-wart combo...

    Anyway, what ever works easiest (and safest) for the OP is good...

    Mal.

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    Quote Originally Posted by Dimal View Post
    Even tiny SMPSUs that I've seen cost more than a relay/base/wall-wart combo...

    Anyway, what ever works easiest (and safest) for the OP is good...

    Mal.
    Agreed except your still going to need a 12v supply for the leds regardless. My point is powering the supply from tappings parralel to the element negates the need for an additional relay.

    And there are plenty of switching 240v to 12vdc supplies on ebay for 4 bucks.

    EDIT: I re read the ops post qnd it would appear they have 12vdc already available so yes dimals sugestion of a 240v coil voltage relay is a good option.
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  13. #13
    Mal Dimal's Avatar
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    Quote Originally Posted by koshari View Post
    EDIT: I re read the ops post qnd it would appear they have 12vdc already available so yes dimals sugestion of a 240v coil voltage relay is a good option.
    Yes, I had noted that initially...

    Mal.

  14. #14
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    Behmor Brazen - $249 - Free Freight
    Quote Originally Posted by Dimal View Post
    Yes, I had noted that initially...

    Mal.
    Tapatalk forum runner sometimes a little clunky.
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