# Trying to wire in LED to show cooker element is on/off

Hi I'm a mechanical engineer so please bear with me. I'm trying to wire in an LED to show whether a cooker element is on or off. Looking at the diagrams below, the easiest way to do this would be to wire an LED into the Aditec MKA-120 outputs between 06 and 07. Would it be that simple?

The images of the diagrams are below:

Internal switchboard: https://imgur.com/mpMYTDU External switchboard: https://imgur.com/GmqQpgk Aditec MKA-120 controller: https://imgur.com/uZ0zAjH Electric diagram for cooker: https://imgur.com/uOERoYz

• Welcome to EE.SE, Charlie. Your question hasn't attracted any comments or answers after an hour. That's unusual for this site so I suggest that the question full of links and no photos may be asking a bit much from your readers. You can embed photos - I think there's a limit of two for new users - and you could format the links properly using the [Description](http://website.com/folder/page.php) syntax (or use the link button on the editor toolbar). Make it easy for your readers. – Transistor Jan 24 at 22:35
• @Transistor thanks for the heads up. I will try redo it. – charlieS Jan 24 at 23:22
• could you use a neon indicator instead of an LED? I have some NOS that is rated 240VAC – jsolarski Jan 25 at 0:33

I doubt very much that an LED is appropriate in this case. All wiring except the temperature sensor is AC line wiring. In particular,06 connects to L1, the active AC line. Anything you connect to this will operate from 230 VAC. In this case, 07 is in series with the heating elements -81 and -82, so placing an LED across these contacts will result in 230 VAC appearing across the LED when the heater is not active.

While it's true you can do this, keep 3 things in mind.

1) You must provide current limiting to the LED, and this will dissipate much more power than the LED.

2) You must provide a diode to protect the LED from the reverse voltage (about 320 volts maximum) which will appear 50 times per second.

3) Because you will have connected directly to line, unless you know very clearly what you are doing, you stand a distinct chance that your modification will cause the cooker to become live, and for your body (or that of someone you know) to complete the circuit. This is called "auto-Darwination" and it is not a good thing.

• Won't the reverse voltage only appear 25 times per second? – Simeon R Jan 25 at 0:27
• @SimeonR - Nope. UK power is 50 Hz. That is, one positive half-cycle and one negative half-cycle every 20 msec. – WhatRoughBeast Jan 25 at 0:29
• Fantastic explanation, love the last bit. Few questions if you don't mind. Can I use a neon indicator instead, as mentioned in the comments above and not worry about current limiting and diodes? Also, you say 230VAC will appear across the LED when the heater is not active, but how can that be possible if the switch is between 05 and 06 and only supplies power to the heating coil when it switches to 06 and 07? If the switch is between 05 and 06, won't the circuit between 06 and 07 be open and any light wired between them is off? Or have I misunderstood the diagram? Thank you – charlieS Jan 28 at 17:56
• @charlieS - 1) Yes, a neon indicator is an excellent choice, but you do have to worry about a current limiting resistor. However, many neon indicators will have the resistor built in - check the data sheet. No diodes needed, since a neon works with both polarities. 2) No, 05 is not connected to anything. When 05 is switched to 06, there will be ~230 VAC between 06 and 07, which will light a neon. The voltage will be reduced a bit by the resistance of the heater elements, but that will be negligable for the currents a neon indicator uses. – WhatRoughBeast Jan 28 at 23:35
• I realise I thought one thing but wrote something else. If I put a light between 6 and 7, I am essentially short circuiting between 6 and 7. I need to put an LED in series with 7 and the coils so when the coils are powered, the light comes on! – charlieS Jan 30 at 1:24