Photon - Power Shield - Power Fault?

Hey folks,

Hoping for a quick sanity check. I am thinking I am attempting to juice too much power through my power shield with the adapter I have. Thoughts?

Set UP
Photon in a Power shield outputting power to an LED Amplifier. The LED Amplifier pushes approximately 17’ of LED lights @ 4 Watts/foot for a total of 68 Watts at 12V DC. I am using a 12VDC AC/DC adapter with max output of 1 Amp. Is it possible that the LED Amplifier is requesting more power than it can get from the Adapter through the Power Shield? In other words, do I need/can I use a bigger adapter (1.2/1.5 AMP) to power the power shield or should I just say forget it and give the LED Amp a dedicated power source?

I know you can’t see where all the wires come from/go in the pic below but you can see how I’m using the power pins to power the LED Amp. I am just using a barrel connector to power the shield from the aforementioned adapter.

That means, 12V @ 5.7A!! So how do you propose to get 68 watts from 12V @ 1A? So basically, you can’t get exceed power (voltage * amps) from what is provided. I would suggest you power the LED Amplifier (separately) and power shield from a single, larger 12V supply. I suggest 12V at 8A or more just to be safe.

BTW, for clarification, the shield the photon is sitting on is not a Particle Power shield.

The LED AMP doesn’t need to take that much input from the way I understand it. The LED AMP can output 6A per channel (3 total channels) and while I do have 17’ total LEDs I have 12’ on one channel and 5’ on the other so I am splitting that load across 2 channels greatly reducing the per-channel requirement.

I can’t seem to find in the LED AMP Specs what the input requirements are. But the LED AMP can output a total of 18 Amps and I can’t imagine providing it that much power.

Another way to ask this is what’s the max current the Power Shield can handle as a pathway (not provided to the photon)? Furthermore, regardless of that max, how can I tell what the LED AMP’s power input requirements are?


@srfnmnk, You seem to be missing the point about “power”. Power is a product of current and voltage. Since the voltage remains at 12 volts, regardless of how many channels the LED AMP can split over, the TOTAL current and hence, power remain the same. As such, the 12V supply powering the LED AMP needs to supply the max current you expect all channels to draw. Since that sounds like 5.7Amps, you need your supply to provide at least that much.

I highly doubt that the PCB traces on the power shield are rated for 5.7Amps wo you will need to power the LED AMP from a separate set of wires, NOT going through the shield. Does that make sense?


You need to put at least the power into the board that you want out on the other side, otherwise you’d already be a rather rich man :wink:

HAHA I like it! And that makes sense but I thought AMPs were able to collect power of multiple cycles into capacitors/transistors and burst out higher outputs than what you’re providing as an input…I though that was the whole point of an AMP, no?

Yes @peekay123, I undoubtedly have a lot to learn about power yet.

@srfnmnk, the actual name for the LED Amplifier includes “(Repeater)” in it. The module is designed to take PWM inputs (possibly from a long set of wires), clean up the signal and drive up to 6 LED channels at a max 210watts. No capacitors or transistors or black voodoo magic that takes power from the air. These boxes are used to locally drive LEDs since long wires for power create loss whereas long wires for PWM signals are more forgiving.

So then to be safe I should be using something like this, agree?

Yup :wink:

Not really that way.
The conservation of energy is a fundamental law.
Amplifiers are never generating energy (which would be the case when you get out more than you stuff in).
When we electronics guys talk about amplification we usually only amplify either voltage or current and most the time not even that directly :wink:
We use transistors to “amplify” a small signal by using that signal to switch a more beefy source which gives us the more powerful output. But the source has to provide us with something to switch in the first place.

And the other thing you mentioned

This is what we see in step-up converters but they (most commonly) only boost voltage but reduce the current in the process. The product of voltage x current will always be (equal or) less than what the contraption takes in.


Good to know. I thought “collectors” collected “current/voltage” for x cycles and released every y cycles…For example, if a capacitor was receiving 12VDC at 60hz then I thought it could store for 4 cycles and release every 5th such that it takes in 60Hz and releases at 12Hz but with a much higher payload. I get there is minutia to the example but basically, I thought that’s what it did.

Hmm, if you mean “collectors” as on a transistor, then no not like that :wink:

As for caps, yes, they can do that (but not for a 60Hz signal and not without a transistor to control the charge/discharge), but as you said “store for 4 cycles and release every 5th” does not increase the product of power x time.
When you average out the power output over the entire time you will be left with (equal or) less of the power you fed into the thing.