Is there anything you want from a Pi shield? Power, relays, etc


#1

I finally got my prototyped Pi printer shield baked. By no means is it perfect, but here are the features:

  • input voltage designed for 12v-24v, has a voltage regulator to push 5v to the Pi (no USB power). Pretty good power conditioning.
  • Relay connected to a GPIO pin. Connected through an optocoupler, so you can safely switch your printer with it.
  • Four GPIO-switched FETs, lowside-driven (so, switches ground on/off, use whatever voltage you want, probably the 12/24v). Designed for 2A max, has overcurrent, overtemperature, overvoltage protection.
  • On-board temperature sensor (good for environmental sensing).

There's also a provision for a fan controller and 3-pin fan port, but I haven't connected those.

I'm going to build and test a couple of these, and I have the next design already in the hopper. I've simplified some of the parts and made it so I can surface-mount solder everything -including the big capacitor, the 2x20 pins for the Pi, the screw terminals, and so on. Those add a lot to the cost (about $10), so I have it set up to also have the proper holes if someone wants to finish up the soldering themselves and save some money.

This is designed for Octoprint; I somewhat assume there's enough interest that I could do a small run of them- my minimum goal is about 8 boards. A board will cost about $20-40 depending on how well the pricing works out- it's not intended to be the cheapest way to get the job done.

So, if you're interested, what features would you like to see added? 5 fan controls? SSR drivers? High-power LED drivers (with an off-board connector)? Thermocouple/thermistor inputs? Off-board temperature/humidity sensing? LED indicators? Panic shutdown switch?


#2

Its a bit more than I am looking for.. Would like a plugin that would set a pin on the PI to high when the selected layer is started and go low when second layer it reached or print ends..
I can build my own driver for a fan relay.. want to run and external fan after most of the support is complete for miniatures.. too much cooling too soon can cause support and then print failure but for the fine detail, the cooler the better. For now I try and remember to flip the switch :wink:


#3

@airscapes Can't you set that with your slicer?


#4

You might be able to achieve this with the OctoPrint-Enclosure plugin or the LEDStripControl plugin. Probably the later is the simplest and would fit the bill. You would just have to set what pin to use and figure out the high/low stuff. My assumption would be M150 by itself is off and M150 R255 would be your high.


#5

Thanks! I will take a look a those plugins..


#6

Looking good so far!

1 relay + 4 fets will meet most ppl's needs I think, but it is a bit limited for me personally. I've currently got 1x relay for psu(s), 1x ssr for enclosure heat, 6x fets for cooling fan, e0 fan, exhaust fan, recirculation fans, ramps fan, and strip leds, one pwm out for a spotlight led driver, and 2 dallas temp sensors for room and enclosure. Of course no sense in trying to integrate an SSR or relay (keep away from hvac anyways... your board would need isolation slots at very least... I'd just avoid the liability if I was you).

Having all those gpio's exposed with 6xfets would be perfect for me, but maybe a bit overkill for most. I think a key feature would be breaking out as many gpio's as you can on a 4x Dupont header, with rows of gnd/5v/12v/gpio (like an rc vehicle rx has but with an extra row for 12V). That would allow flexibility to add powered stuff if needed (add on fet/relay boards with 5v optocoupler drivers, prox sensors, dallas temps, etc). 4 fets should meet most needs, but some like me will want more (think of folks with rgb strips... there goes 3 fets before fans are even added).


#7

Hmm, I see what you mean. Sort of like a servo shield with all the rows of pins.

Yeah, One thing I can do fairly easily is design a board and then only partially populate it- in other words, if you don't need a dozen FET drivers, it might save about $1 per driver to leave them off. Having additional boards would be fine- but it doesn't seem like there's enough volume for a base board.


#8

Not sure if this is a big thing, cuz I've already addressed it (the hard way) but, I need to power both a 12v set of lights, and a 5v relay. The way I'm doing it now is to use two HATS stacked on top of one another. I only did it that way cuz I happened to have that stuff on hand, but, it seems like there should have been a way to do it with only one HAT


#9

Yeah, the onboard mosfets would let you do that. They switch between (say) your lights and ground, so you can set 'positive' to either the 5v or 12v.


#10

But I need to control both individually


#11

my board has 4 little mosfets- so 4 individual channels.