Connecting LEDs to Power Supply
Hi all,
I'm looking to light up the Mk3 with some white LEDs (bought these ones: http://a.co/e8Pt4Vi ) and I was considering trying to power them through the Prusa with a switch instead of using a wall outlet.
I thought I read somewhere that this was doable on the Mk2 but I'm not sure about the Mk3. Additionally, do I require any additional hardware to ensure that I don't pull too much power from the power supply (voltage regulator or something)? I'm not too electronically saavy so I apologize if these are stupid questions.
Thanks!
Re: Connecting LEDs to Power Supply
Do you just want on/off functionality? You could just use an inline switch (i'd add a potentiometer too) with a strip of leds by hooking up to vcc but i'd want to see how the circuit behaved under load, i haven't looked at this much but if i were to guess what my ideal situation would be is to put a arduino pro mini on vcc so that the draw would be on the power supply.
could someone correct me if i'm wrong but i'm thinking this is the new einsy in the MK3? http://reprap.org/wiki/Rambo_v1.3 might be this mini, i'm a little unsure: http://reprap.org/wiki/MiniRambo
Re: Connecting LEDs to Power Supply
I was thinking of at least on/off capability, but if I were smart, I'd like to use my Pi0 (or the Einsy) to control the lights on when there's a print going and off when there isn't.
Re: Connecting LEDs to Power Supply
Also, although it's not everything, this might help with distinguishing the Rambo: https://d17kynu4zpq5hy.cloudfront.net/igi/prusa3d/4YobwHH2WD64Aler.huge
Re: Connecting LEDs to Power Supply
There are a number of ways to control externally powered LEDs by using a low voltage controlled relay. All depends on what you want.
I would however NOT recommend using the MK3 to power any external lights. I would use a MK3 activated relay control and another external power source for that.
Maybe this will spark some ideas!
https://www.pololu.com/category/135/relay-modules
Or TTL logic controlled:
https://www.superdroidrobots.com/shop/item.aspx/10a-relay-controller/1961/
MK3 Kit, Designed, built 4x4 CNC Plasma Cutting Table, Motorcycles Bigdogbro's Adventures
http://www.youtube.com/channel/UC5djrxBeeOKB9_6rHnn6G8A
Re: Connecting LEDs to Power Supply
I tied a couple small SMD LED panels directly into the power output on the Extruder side of the power supply, just slide a 18 gauge wire in under the lugs. The LEDs pull very little power. So the lights are controlled by the main power switch. Helpful way to remember the printer is turned on, although the printer only pulls about 8-10 watts while idle. Robbing a couple watts off the main power supply should be no problem, when the printer is running PET (245 extruder /80 bed) it is only using about 100 watts. What is the rating on the PSU? I am in the middle of a print, or I would take a look.
There is are couple Octoprint plugins that can control lights and relays. I bought a 4 channel Sainsmart relay to play with, but just haven't got to it yet.
Re: Connecting LEDs to Power Supply
On the whole i would agree with DogBro, and do so at your own risk; however, if you're feeling invested and want to give it a go, you can look at the max draw the components are rated to, and the energy potential of the power supply and calculate the potential draw of your lights using ohms law (more on that here), if you are still well within the rated power consumption per the technical data, i would probably do it. At the very least i would check the power supply on a multimeter and see how much draw is on it during different tasks or better yet, a oscilloscope but i realize that may not be practical.
Re: Connecting LEDs to Power Supply
The power draw numbers I mentioned above were measured with a Kill a Watt P3 main line meter.
Re: Connecting LEDs to Power Supply
The power draw numbers I mentioned above were measured with a Kill a Watt P3 main line meter.
Just given that you can easily pop the pi in there and use the IO i would likely do that via octoprint, even if it didn't give you the control you wanted you could control something else with i2c which probably would.
Re: Connecting LEDs to Power Supply
Don't expect the POWER RECOVERY feature to work if you do connect any additional major power load to the MK3 power supply.
MK3 Kit, Designed, built 4x4 CNC Plasma Cutting Table, Motorcycles Bigdogbro's Adventures
http://www.youtube.com/channel/UC5djrxBeeOKB9_6rHnn6G8A
Re: Connecting LEDs to Power Supply
So it'd be (maybe?) that I'd hook up a relay to one of the pins of the Pi0, then use gcode (?) to control that pin on and off? Am I understanding things correctly or am I out in left field?
Re: Connecting LEDs to Power Supply
So it'd be (maybe?) that I'd hook up a relay to one of the pins of the Pi0, then use gcode (?) to control that pin on and off? Am I understanding things correctly or am I out in left field?
Correct, you could do that. The relay CONTROL logic level input is TTL logic compatible from a normal control board but the power to run the LEDs should come from an external wall wart power supply thru the relay contacts.
That one listed relay board needs 24 volts run to it just to operate only the relay coil which is most likely under 100ma on the DC 24v MK3 supply. The user control comes from either an Einsy I/O pin or from the I/O of the PI Zero bd. However you are able to write code to actuate the I/O.
Vcc: Coil Voltage (if you are using a 24V coil, hook 24V up here, its what powers the coil and pulls in the contact)
https://www.superdroidrobots.com/shop/item.aspx/10a-relay-controller/1961/
You will need a cable like this to connect to the vertical 3-pin header on the relay board. (GND, TTL, 24V)
https://www.superdroidrobots.com/shop/item.aspx/hitec-jr-airt-18in-extension/501/
You may need to solder some parts to the board.
MK3 Kit, Designed, built 4x4 CNC Plasma Cutting Table, Motorcycles Bigdogbro's Adventures
http://www.youtube.com/channel/UC5djrxBeeOKB9_6rHnn6G8A
Re: Connecting LEDs to Power Supply
Side note, power recovery doesn't work with Octoprint anyway due to firmware issue, might eventually be rectified though.
Re: Connecting LEDs to Power Supply
Don't expect the POWER RECOVERY feature to work if you do connect any additional major power load to the MK3 power supply.
I don't think that using it will affect this function. Needed power for this function must be held at low voltage section of MCU (5V). It's common practice for this function to design power supply in a way that a part of 5V supply is fed through diode and it's reserved only for MCU, which draws very little current. When power-off occurs there's really not enough time for MCU to do all disconnection commands - those are already shut off immediately when power-off occurs. A diode prevents 5V to keep up powering MCU only to be able to write necesarry data to EEPROM.
Re: Connecting LEDs to Power Supply
Has anyone worked out if there are any expansion pins available on the Einsy board?
I was watching one of Tom's videos and want to try this:-
He suggests using pins 54 - 69 (A0 -A15) but having looked at the Einsy schematic it appears that none of these are connected to any sort of expansion connector that isn't specifically being used. 🙁
Re: Connecting LEDs to Power Supply
Could you tap into one of the 5v fans power? I just want a few LED on the extruder.
Re: Connecting LEDs to Power Supply
I guess you could if needed current will be small enough. I connected extra fan on 5V from pinda probe to coll down extruder motor. I used small 5V fan (30x30mm) requiring under 100mA. I guess that going up to 100 - 200 mA would still be acceptable.