In short, is it possible to drive the following using a single power supply:
– Plasma Stick 2040 W
– 80 SK6812 RGBW LEDs (5V 24W)
– 24V 2A in short bursts (500ms long every minute) with reversed polarity every other burst.
If so, what voltage and current should the power supply be (5V or 24V) and what components should I use (step-down, step-up, H bridge) and where in the circuit? Thanks.
You want 5V not 24V. To supply 24 Watts @ 5 Volts your power supply needs to be able to supply 4.8 Amps. Might as while say 5A as some will be needed to run the Plasma Stick.
And why the reverse polarity?
I actually got a dual 5V 6A / 24V 2A power supply for the project but I’m not sure if it’s possible to power Plasma through the LED terminal? Kinda would be obvious but I don’t want to damage the board.
Pin 1 , the one marked (5V+) is connected to VBUS. Feeding 5V in there will power the Plasma Stick and the LED string.
plasma_stick.sch (shopify.com)
EDIT: If you do that you want to be careful when you connect it to your PC via a USB cable. You will have to turn off the power supply connected to the 5V+ pin. If you don’t the two power supplies will fight each other trying to regulate the voltage.
Thanks, will keep that in mind. Will I be able to test 60 RGBW LEDs via USB, though?
I’m running this via USB off of an official Pi Power supply with no issues.
Wireless Plasma Kit (Pico W Aboard) – Bring Your Own Bottle (pimoroni.com)
EDIT: I don’t remember having any issues with it plugged into my PC’s USB port? If it’s a USB 3 port I would think you’d be fine? I wouldn’t go full bright and all white. ;)
I have an Interstate 75 setup with a 64 by 64 LED matrix. I run it via a 5V 4A power supply wired to the power studs on the Interstate 75. There is no way this will run just from the USB power port.
What I did was modify a USB cable and cut the Red +5V wire. It’s now Data +, Data -, and Ground only. I can plug that custom cable in for programing and not have to unplug my power supply.
Thanks, that’s a great idea!
Re reverse polarity – that’s how the old railway clock’s mechanism is powered. See here. The question is can I add anything to Plasma Stick beyond the QW/ST connector (to which I have attached RV3028 RTC), e.g. a motor driver? I’m thinking of something like this one. If yes, how can I control it with MicroPython?
As a side note. You can have multiple devices on i2c, as long as no two devices have the same i2c address. I don’t see anything Pimoroni offers that will work with that voltage though.
An H-Bridge Motor controller would be a good way to go, and the one you linked to will handle the voltage no problem. Getting the PWM setup may be a pain. I don’t know how to do it. It’s not something I have ever attempted.
I am afraid the answer is no. The Plasma Stick only uses a few pins of the Pico and it is a shame that Pimoroni did not add an extra 2.54mm on both sides to break out all the Pico pins.
One suggestion: build your own! You need a normal Pico W and a level shifter for the data-pin. That’s about it.
A shame, indeed. But, in theory, could I try soldering something to one of the pins even if not exposed properly? I found this post where it’s suggested any pin could be powered on and off with something like x = machine.Pin(10, machine.Pin.OUT) x.on() x.off(). Is this true? The thing is I’ve already bought two Plasma Sticks and need to make them work no matter what! Thanks.
Yes, you could try to solder something to these pins. The only realistic chance I see is to add pins or sockets sticking out horizontally. Put a cardboard or some other PCB next to the stick, tape your pins to this helper-board and then try to solder. I would go for a large number of pins even if I would only need two because this will increase mechanical stability.
Good luck! And please post images. It would be great if this would work.
(Another option would be SMD-pins, but I doubt they will help in this case. Have a look here: pcb-badger2040-wlan/badger-with-smdpins.jpg at main · bablokb/pcb-badger2040-wlan · GitHub).
If it was me I think I’d go with right angle.
Solder the ones you think you can use then break the header.
Break Away Headers – Right-Angle (pimoroni.com)
It is even simpler. The Pico (W) has an enable-pin, if you pull it low e.g. with an external button, it will turn off.
Similar thread, with button info and code.
Plasma 2040 Button & Code Assistance - Support - Pimoroni Buccaneers
Just checked: although soldering might work, you have mechanical strain. With straight headers, your force while plugging/unplugging is not orthogonal to your soldering.
The advantage of the enable pin is that you don’t need a single line of code to make it work.
Can you elaborate on the code you have in mind? In order to control the clock, I’d need to toggle two pins HIGH and LOW every minute.
I was thinking something like this
L < header
_{pico}_
L{pico}_
