Combined thyristor circuit, will it work?

Discussion in 'The Projects Forum' started by rp211922, Jan 10, 2011.

  1. rp211922

    Thread Starter New Member

    Jan 10, 2011
    I have no one in my surroundings with the proper knowledge to check this circuit for me, so I'm turning to you guys.
    My current project is a fantasy inspired "arm": A simple cotton glove with foam "plates" over it, painted with liquid latex. The back of the hand is going to be inlaid with two different colours of EL wire and the palm is supposed to hold a small cluster of bright LEDs. The result is supposed to be a stone-arm with runes that can glow in two different colors and a flashlight built into the palm.

    I've done stuff like this before so this isn't really giving me a headache. The switches, however, are. With my previous projects I had tumbler switches build near the Driver to turn the entire thing on and off. This time, I've decided to use a single EL Driver to minimize the weight. As a result, I have to built in three switches to turn on the different components (Red EL, Blue EL, LEDs). I decided it would be cool is I could place the switches under the foam on the side of the index finger and be able to control the entire glove with just my thumb. The only buttons I found that could be pressed whilst being under the foam and were small enough are those small Momentary tactile buttons you see in handheld videogames and such.

    This, of course, led to a new problem: I really don't fancy pressing my thumb against my hand continuously to keep the light on. After a bit of looking around I came across the Latching thyristor circuit.

    I've made a circuit design, but I'm not sure whether it works or not. As for the parts:
    - The 1k Ω resistor is in place to protect the gate of the thyristor
    - The 100Ω resistor is a placeholder. I don't have a multimeter handy to measure the output of the drive so I'm not sure how much Ω I'll need.
    - Top button's supposed to turn on (and keep on) the red EL wire after being pressed once.
    - Middle button's supposed to turn on (and keep on) the blue EL wire after being pressed once.
    - Lower button's supposed to turn on (and keep on) the LEDs after being pressed once.
    - the Push-to-break switch it supposed to interrupt the circuit and reset the thyristors, effectively resetting them and turning the lights off.
    - The switch near the EL driver is a safety control in case things go wrong, it'll be in an easily accessible place to immediately interrupt the circuit.

    So, I ask you, will this circuit work?

    Thanks in advance for reading.

    P.s.: I read that you guys prefer attachments as PDF.

    Small update: Someone pointed out I had the gate connected to the ground. I've made a new design whit the gates lined up correctly. The new drawing is the first drawing in the PDF, the old drawing is the second drawing in the PDF.
  2. jason 77

    New Member

    Jul 27, 2009
    I have never delt with thyristors before, but I do know that "EL drivers" outputs are like 160-180+ volts. I would suggest running a seperate power line for the LEDs from whatever power source you are using. Also I am not sure but I thought that you have to have a load of some sort connected to the EL drivers otherwise they will fry them selves if you apply power to them?
  3. rp211922

    Thread Starter New Member

    Jan 10, 2011
    I wouldn't be surprised if the output voltage was that high, it's still elektro-luminescence through phosphor in the end. As for the LEDs: I've connected a driver to 3 LEDs in series with an adjustable potentiometer, it worked quite well, although with that voltage, they'd probably burn themselves out, right?

    As for the load on the driver: If you don't have a load on them they work like any other charger left in the wall socket: they heat up a bit and that's it. I've accidentally left one on for a day with no consequences to the device whatsoever.

    Thanks for the insights, though.

    Update: Found a fundamental flaw in my own design. Thyristors won't work with AC, they'll turn themselves off almost immediately. EL won't work with DC. Back to the drawing board.
    Last edited: Jan 10, 2011

    Senior Member

    Jul 1, 2008
    The term 'Thyristor' denotes a family of components, some intended for DC and some for AC. A Triac is a Thyristor that's widely used for AC control but will work with DC too.
  5. rp211922

    Thread Starter New Member

    Jan 10, 2011
    Thanks for the suggestion Cdrive, but I've chosen to separate the systems into a low-current DC circuit and a high-current AC circuit and "connected" them using a SSR kept on by a Thyristor (SCR). This one'll probably be easier for me to make and it makes sure the LEDs won't get fried.

    If anyone cares to give the new design a quick look, it'd be much appreciated. First pic's the bare circuit design, second is color-coded for my personal convenience (and I'm sure there's somewhere out there who likes fancy colors)