Overcurrent error
I have a slightly advanced case... I'm driving a RPi off the same power supply as the printer. I attached wires to one pair of red/black terminals in the power supply. I then run those wires into this buck converter: https://www.amazon.com/gp/product/B019RKVMKU to reduce the voltage to 5V for the RPi. The output from the converter powers the RPi great.
HOWEVER on bootup... if I have the buck converter enabled I get this error: https://help.prusa3d.com/article/mmu-overcurrent-13310-mk4-21310-mk3-9-23310-mk3-5_405620
If on the other hand I toggle the buck converter to off and then start the printer everything works fine. I can then toggle the buck converter to on and everything works as expected.
My questions are:
1. Is this setup a bad idea or no longer supported? (I ran a similar setup with my MK3S+/MMU2 without problems)
2. Is there some way to wire differently to avoid this error (I tried both red/black poles and it didn't make a difference)
3. Is there a way to disable this error code?
It's not a huge pain to have to remember to turn the printer on with the RPi turned off, but it's a minor annoyance I would prefer to avoid if possible.
Thanks!
Andy
RE: Overcurrent error
The error is probably because the PSU has to build up voltage in both convertor + board at the same time. There are capacitors what have to be loaded.
This takes too long for the safety management, so it throws an error.
You could solve it with a separate PSU (not what your are looking for) or
Find a way to delay the start of the buck convertor. A small relay (capable of switching about 10 Amp for the Raspberry) with a delay circuit (can be very simple) to start it 1-2 seconds later would probably do the job. Search a bit on internet, and you will find cheap simple solutions for that. (you have to solder it yourselves).
We will do what we have always done. We will find hope in the impossible.
RE: Overcurrent error
Awesome! That sounds just like what I needed to learn about. If I'm correct from the readings and videos I've considered then something like this should do the trick. https://www.amazon.com/dp/B00LW2VLS0/. Does that sound right? Thanks a lot!
RE: Overcurrent error
I do not understand what that module exactly does. Seems mostly to be a switch (controlled with button or line) to switch high load.
Have a look at this please: https://www.amazon.com/NE555-Switch-Adjustable-Module-Shield/dp/B0CJ828X5B
VCC of timer is connected to 12 Volt. The timer (run on NE555) has to be set to about 1 second.
VCC is also connected to the relay. The other side of your relay goes to the buck-converter.
Ground is just connected to both : ground of timer and ground of buck-converter
We will do what we have always done. We will find hope in the impossible.
RE: Overcurrent error
Oops. Not sure how I posted the wrong link, but I thought I was posting something like you linked... Thanks again. I'll report back how it works.
RE: Overcurrent error
OK... I got it working briefly... The printer turned on. There was no MMU error, the timer fired after about 1sec, the RPi turned on.... yay! However on the second reboot there was a poof of smoke and I the timer chip looks fried. I think this is because the power coming out of the printer is 24V and that board is rated as 12V.
Luckily I order 6 of the boards... So I tried power supply to buck converter (as was originally the case on my MK3S+) to timer/relay board and then timer/relay board to the RPi. The printer powers up as expected (no MMU error), the buck converter is lowering the voltage to 5V and the VCC LED on the timer/relay board comes on but the timer triggers. I think this is because 5V isn't enough to power the timer on the 12V board.
I think if I get the 5V version of the board ( https://www.amazon.com/dp/B08YYMF4M5) that this second schematic will work and the problem will be solved. Does that seem right?
Thanks again for your tutoring!
Andy
RE:
Ai, you never want smoke! OK, so 24 Volt is too much and 5Volt is too low (it will not activate the relay).
The link to Amazon is "dead", but I think I understand what you want to do. And that will work OK.
An another option is to lower the voltage to the switch PCB. Because the Switch it self only uses low amperage, this could be done with a zenerdiode (of about 12 Volt) in series with the PCB (you have to check the amperage of both!).
My calculation on the back of a beermat: with 12 Volt it will have an amperage around 200 mA.
The zenerdidode has to dissipate 12 Volt x 0,2 A = about 2,4 Watt)
So something like this will do https://www.amazon.com/BOJACK-1N5349B-Power-Diodes-1N5349/dp/B07X7VJ7ZC
The 24 V has to go directly to the relaycontacts and the buckconverter. (not through the zener)
NB: Take care the zener is freely mounted so it can loose its temperature.
We will do what we have always done. We will find hope in the impossible.
RE: Overcurrent error
Thanks for the zenerdiode idea and link. I think I'm going to try the different switch and ordering and see how that goes. FWIW the correct link was this https://www.amazon.com/dp/B08YYMF4M5 the forum software treated the parentheses as part of the URL. I appreciate the help!
RE:
I got it to work (no smoking chips either lol). Power -> buck converter -> timer switch -> RPi works great. One thing I noticed is that if there is a power blip the printer will reboot, but the timer switch doesn't have enough time to discharge and reset. So for a very short power outage it is still possible to get the MMU overcurrent error. But generally the problem is solved. Thanks for the lesson @Eef!
Andy
RE:
Great it worked:
To get it to discharge faster add a 330 ohm between + and ground of the timerswitch. With 24 Volt this give a continuous amperage of 70 mA. Power consumption in the resistor wil be about 2 watt, so choose one what is big enough, but it helps unloading the capacitor.
We will do what we have always done. We will find hope in the impossible.
RE: Overcurrent error
PS: test, maybe even a smaller resistor of 1 Kohm is enough
We will do what we have always done. We will find hope in the impossible.