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touch button power switch circuit
touch button power switch circuit
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Old 20th January 2003, 01:44 PM   #1
vossie is offline vossie  Israel
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Lightbulb touch button power switch circuit


I'm interested to use a "reset" type switch to fire up my Aleph 5 but don't have the electronic expertise on how to design a small circuit to use this kind of switch.

To make my question a bit clearer: The "reset" type switch only makes contact for as long as it is depressed, therefor I would need to use a relay (I suppose) for the main switch. How do I fire up a power-switch curcuit using a "reset" type switch?

Any ideas?

The brave might not live forever but the cautious never live at all!
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Old 20th January 2003, 02:11 PM   #2
RKC is offline RKC
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Most of the large industrial equipment I work on is set up this way. However they use 2 separate buttons one each for on/off. The "On" button needs to be N/O, it ties to the coil on the main power relay. The off button must be N/C and ties between the N/O relay contact and the coil. In this way when you press the "On" switch the relay makes. Releasing the 'On" switch doesn't deenergize the relay as its supplying its own power from its N/O contact.
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Old 20th January 2003, 03:06 PM   #3
Smithers is offline Smithers  Germany
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if you want to use two buttons, you can use a relais. Once pressing the on button it holds itself in on-mode. A switch which opens when pressing can be used to disconnect the relais from the power. I suppose you will need an ic like a flip-flop when you want to use a single switch, or am i wrong?
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Old 20th January 2003, 06:40 PM   #4
PedroPO is offline PedroPO  Portugal
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I used a finder relay for my aleph 5

only a momentary push button is required.

make a search on "pulse power switch"
or "finder" and you shoud find my previous post.

there is its part number and I believe the price.

If you don't find, ring again and I'll look into it.
Pedro Oliveira
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Old 20th January 2003, 07:20 PM   #5
Possum is offline Possum  United States
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From the thread PedroPO is referring to, I ended up buying a Potter & Brumfield (of Tyco Electronics) bistable impulse relay:

Spec sheet:

You can figure out what part number you need at the bottom of the first page of the spec sheet. I ended up going with the 120VAC operated version (for use in the USA) with 20A contacts bought for about $35 from here:


The design of the relay assembly is pretty straightforward and is amusing to watch for the first few operations.

For my momentary push button, I used a Vandal switch from Bulgin (www.bulgin.co.uk), the MP0031 for my 1/4" (6.35mm) front panel, purchased for ~$14 from www.newark.com. I picked up the Vandal switch hint from a thread where an Aleph used one obtained from Conrad.
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Old 20th January 2003, 08:00 PM   #6
mirlo is offline mirlo  United States
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touch button power switch circuit
Default One could also ...

build a low current rectifier for the AC line, zener regulate some voltages, using LARGE resistors, and use power mosfets for switches. Of course, this is troublesome because you need to put 2 mos in series for each switch to prevent the bulk diode from conducting, and (I think) you'd need both PMOS and NMOS...

Has anyone done this with FETs?
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Old 20th January 2003, 08:13 PM   #7
jackinnj is offline jackinnj  United States
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touch button power switch circuit
Default just use a flip flop

you need a little "debounce" on the switch (which can be a little RC network) the first push of the switch "sets" the flip flop and the next pulse toggles it to "unset" -- flip flops cost about $0.25. Of course, the f/f should drive the base of a transistor as they won't handle a lot of current.<p> You can also use a "momentary off" or "momentary on" switch.
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Old 20th January 2003, 08:37 PM   #8
LBHajdu is offline LBHajdu  United States
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I to want to control my amps with a low power easily pushable momentary contact switch.
My AX amps will have a power supply in a separate case to keep the amps cooler. Each amp will have a button on it that turns all the amps on with one push and then turns all the amps off with another push. I have really no electronic expertise, but even I can figure out how a relay works. So after using up a lot of scrap paper I finally figured out how to do it . My circuit uses two latching relays in a type of flip Ė flop. The relays go throw 4 cycles, two turn the amp on and two to turn the amp off. All that clicking inside should sound really neat. I donít like using semiconductors, the relays will last longer. I have not tested this idea, but I believe it will work, because there is very little that could go wrong. I have not filled in any of the values, even people without electronic expertise should be able to figure out with they are. If anybody builds this please let me know how it works.

Levente B. Hajdu
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File Type: zip ax power suplly.zip (51.0 KB, 295 views)
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Old 21st January 2003, 01:19 PM   #9
Jason Hubbard is offline Jason Hubbard  United Kingdom
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Default Beware of inrush currents!

If you power up all your transformers simultaneously you'll most likely take out the trip on your fuseboard.

You need a power sequencer to wait a few seconds bedtween powering up each transformer, don't know if anyone has a suitable circuit.

Perhaps you could use some readymade 555 timer PCB's with different delay times on them to fire your relays?
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Old 21st January 2003, 02:16 PM   #10
LBHajdu is offline LBHajdu  United States
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Actually Iím using Nelsons method of using a thermistor on one of the ac lines. Thatís what the resistor you see there is. This method is cheaper and less likely to go bad over time then a whole complex setup with a 555 timer. Question, so why donít more amps use it. Answer, because not all amps draw a constant current and the thermistor needs a constant current to heat up so its resistance can drop. This method should not be used for example with a class d amp.

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