This is my first post here and i was wondering if anyone could help me. I am trying to create a system that will enable me to connect nine or ten 240v devices but only run one at a time. if one in the system is on and another one is switched on the first one will turn off. Is there a simple way to achieve this? I've been searching Google for the last five hours with no success. I'm not sure what I should be searching for or what kind of design can help me achieve this.

I found this on YouTube but I got stuck trying to expand the amount of switches and bulbs.


Thanks for you help.


Hi there. Thank you for the comments. I could do this with a simple rotary switch but I was looking for a solution that was spread out to each device. To give a little more context each device would actually be controlled by a NVR (no-volt release) switch. If we take the example of the YouTube video. And did each switch with an NVR. Then the system would reset its self when ever one of the switches where activated. Why this is useful is so that if the devices are spread out then they can be activated in the knowledge that if another one was on it will be turned off and reset.

And to answer some questions.

Homework? Sorry, this is for a small woodworking business.

The point of this system is not to overload current draw on the main breaker board. If two of these devices are run at the same time then they will trip the system. There is no way to expand the current rating on the main board so this is the only solution to keep the system from tripping out. The devices are power tools (table saw, spindle moulder, lathe etc...) and have been installed with soft starting modules (this is so that peaks don't trip out the breaker board on there own) so it's not that critical that they end and start microseconds together.

Do you know of a way or formula to expand that switch circuit in the video?

  • 4
    \$\begingroup\$ I’m voting to close this question because it's a homework problem with no effort shown. \$\endgroup\$
    – Hearth
    Nov 5, 2021 at 23:56
  • 1
    \$\begingroup\$ How would the system know if you want to turn some device on so it knows to turn off other devices and turn the wanted device on? Is there some user button? \$\endgroup\$
    – Justme
    Nov 6, 2021 at 0:01
  • 2
    \$\begingroup\$ Check this en.wikipedia.org/wiki/Stepping_switch \$\endgroup\$
    – user263983
    Nov 6, 2021 at 0:21
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    \$\begingroup\$ the youtube video circuit does not behave the same way as your requirement \$\endgroup\$
    – jsotola
    Nov 6, 2021 at 0:54
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    \$\begingroup\$ @RussellMcMahon To be fair, it reads quite a bit like a homework question. At least it did when I voted to close; it's been expanded now. \$\endgroup\$
    – Hearth
    Nov 7, 2021 at 23:44

1 Answer 1


Here's a way using 10 push button switches, 10 magnetic latch relays and a diode matrix.

enter image description here

The schematic shows only 3 relays.

'NO' contacts of the relays K1, K2 & K3 are to be used to switch the 10 devices.

Freewheeling diodes for the relay coils and LED indicators are not shown.

However, the above circuit does not satisfy the 'no-volt release' feature which is a must with regard to power tool operator safety.

The following circuit takes care of that, using only standard electromagnetic relays / contactors without retentive latching.

The normal and e-stop push buttons are all of the 'momentary' type.

enter image description here

  • \$\begingroup\$ Thank you for that! Your idea has given me the fuel i need to complete this using No Volt Return switches and standard DPDT relays (i have them already and i also need the NVRs for safety reasons for each machine). I will source some diodes now. once i have it figured out i will add what i did as an answer. Thank you. \$\endgroup\$
    – GammaX
    Nov 6, 2021 at 16:48
  • \$\begingroup\$ GammaX, I'm sorry I missed your 'no-volt release' requirement. The latched relays would certainly be out of question while taking into consideration the safety aspects for power tools. \$\endgroup\$
    – vu2nan
    Nov 6, 2021 at 18:05
  • \$\begingroup\$ Hi Vu2an, yes that is correct. i wont be latching the relays. and i will be using No-Volt release switches with emergency stop buttons for the switches which will work as the latching mechanism. it was the diodes and grid based design that was missing from my own designs. Also, depending on if the relays will natually cut off the NVR switches when changing from opend to closed i may also add a sparate timer relay to delay activation so as to give the NVRs time to activate and close. i will add another answer in a few days once i have had time to implement it and test. Thank you. \$\endgroup\$
    – GammaX
    Nov 6, 2021 at 20:44
  • \$\begingroup\$ Hi GammaX, I've redesigned the circuit to take care of the 'no-volt release' feature. \$\endgroup\$
    – vu2nan
    Nov 7, 2021 at 6:25
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    \$\begingroup\$ @vu2nan, I'm still impressed with your ability (and madness) to create schematics in Paint! Just a point. Shouldn't the NC contacts be mirrored so that the S11, etc., buttons push them open? \$\endgroup\$
    – Transistor
    Nov 7, 2021 at 14:57

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