Any electronics wizards out there..?

I’ve got a couple of (non-latching) switches I use as feed hold buttons, and the specification indicates the LEDs are 12V DC.

I’m using a 12V DC plug-in transformer with 12V 1000mA output, but the two LEDs are very dim.

I seem to recall filament bulbs are normally connected in parallel, but should LEDs be connected in series?


No, parallel should be fine but can you elaborate on the wiring of those two switches in you setup, with closing the feedhold loop on one hand and the separate 12V power supply on the other hand?

With a 12v 1A supply, LEDs rated for 12v should give ‘good’ brightness. How bright will depend on the spec. Dim light suggests one of two things: either that 12v is not the rating, or that the return path (ground or 0v) is not present but the current is in fact flowing into the feed hold input on the ShapeOKO control board - not a good idea in case the input is damaged by this, nor providing enough current ‘sink’ to allow the LEDs to shine.

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You mean there are LEDs embedded in the switches? Are the switches rated for mains voltages? Do they have separate wiring points for the LEDs?

Could you take some photos of your setup?

What I’m thinking is that maybe the switch is intended for mains voltage and the LEDs embedded in it are powered by some small internal circuit which provides them with 12V from 120/240V.

Can you clarify this? A transformer is inherently an AC device, it doesn’t work with DC. By “transformer”, do you just mean an AC/DC converter (power brick)?

That would mean my “mains voltage” idea above is likely bust…

And I had it so clearly in my mind!

These are the switches, which has two connectors for the switch and two separate connectors for the supply to the LED.

The PSU is like this, but only 1A. The LEDs are not connected to the Shapeoko.

I was thinking I might use a PSU like this to supply work area lighting as well as the LEDs in the switches.

The reason I asked about parallel or series is that, when I connected just one of the LEDs, it was quite bright, but with two, they’re both quite dim.

You want to run parallel. You’re splitting voltage running in series. A 1A supply is more than enough for two LEDs.
Just keep the two circuits, led power and FeedHold signal, separate.


Yes, that’s what I thought.

I thought that too, but don’t LEDs work differently to filament bulbs? Aren’t LEDs current specific and filament bulbs voltage specific?

Less voltage, with the same resistance (calculated to make the LEDs “12V”), will mean less current which means less brightness.

Also, why two switches?

Just the design, really. One by the laptop and one just below the worktop, close the cutting area.

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Were they ever bright? Perhaps just for a second when you first connected them? It is possible that if there are no in line resistors the leds could have burnt out pretty quick and dimmed.

Since the switch specifies “12VDC”, that means there are current limiting resistors in the design.

@NewToThis I haven’t seen a schematic of your switch wiring. Does you wiring exactly match your schematic?

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I don’t think the voltage specification indicates any kind of current limitation. He said it is a 1a power supply. Unless voltage drop on the led is equal to the 12v power supply (Or likely higher depending on the quality of the psu) he would need current limiting resistors. In most designs I’ve seen, additional current limited are put in as another layer of protection.

You can put all you want to reduce the current at 12VDC applied, but when it says “12VDC” or some other voltage then there is a current limiting resistor internal to the switch. Trust me.


Yes. These are very common arcade switches. They have a built-in resistor.

With one connected it was brighter than the existing one, so I assumed changing to a slightly more powerful plug-in PSU was the answer - but with two LEDs? Nope!

What @neilferreri said. I’m wondering if they shouldn’t be connected in series, rather than parallel, after all. I’ll check when I get home and I’ve got two spares if I blow them :exploding_head:

Not with a 12v supply. Your 12v 1A supply should be more than enough.

@NewToThis … and still we don’t really know how you actually have wired all this together.

Good point…

The plug-in charger has a +ve and -ve wire connected to a terminal block.

From the terminal block there is a +ve and -ve wire to each of the LEDs, connecting them in parallel.

If I disconnect one of the LEDs, the connected one gets brighter.

I can draw the circuit diagram when I get back to my computer, if that would help.

If one is getting brighter when you unplug the other, and you’re sure they’re in parallel, then either you have a short circuit somewhere or you’ve been scammed on your power supply. The supply isn’t able to source the current required, so its voltage is dropping out. Measure the voltage across your power supply with one and two LEDs connected and let us know what it says.

A red LED typically takes on the order of 20 mA, maybe 100 mA if it’s especially big/bright. There’s no way that your LEDs are rated to draw more than 500 mA each.

Can you try placing a known load (capable of dissipating up to 12 watts) across the supply and see how it behaves? Is it sourcing the current you expect for that load?

Cheap or counterfeit power supplies would be nothing new to Amazon. It’s more likely than the switch/LED not behaving as designed.

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