Altering Ultimaker 2 to open/close solenoid valve for bioprinting

[umnbioprinting 2]

The BioStruder is up and running! I just had to swap a couple cords in the wiring diagram, but now it works perfectly! The solenoid opens and closes with the LED commands from both gcode and the LCD menu.

Unfortunately, my principal investigator doesn’t want me posting any pictures/videos of the alteration until we’ve submitted a paper for publishing (shouldn’t be long). Until then, I am willing to send them, privately, to anyone that helped out here! Just let me know in this thread or in a message, and I’ll share some pictures/videos with you—the only caveat is that I have to ask you to please not share them with anyone until we have submitted a paper for publishing.

I was wondering if anyone had insight into a couple questions I’m still having. The extruder is working great, but I still have one work-around to figure out…the LED turning on automatically when I start a print…this causes the solenoid to open early. I changed the Ultimaker’s LED setting to “Always Off”, and I inserted an “LED off” gcode command as the first thing in the code, hoping it would “head-off” the automatic function that tells the Ultimaker to turn the LED on at the start of a print…but the Ultimaker still automatically turns the LED on the moment I start any print. Is there a way to disable the LED at the beginning of the print? Is this something that would have to be changed in the firmware?

The other question I have might be a simpler one. Now that I have the extrusion working, I was hoping to add a small LED to the end of the extruder for curing the gels (they polymerize when irradiated with a specific wavelength of light). Are there other available outputs on the control board that have the convenient solution of powering on/off with a simple gcode command like I’ve done with the solenoid? As always, sorry if any of this isn’t making sense—let me know if I need to clarify anything a little better. And thanks in advance!

[SyntaxTerror 344]

Good to hear that you've made progress! And not to worry - we're patient people. Just curious ones as well

For comparison purposes - which firmware version is your UM2 running?

Edit: I can confirm that at least with Tinker firmware, the LEDs do not turn on when set to "always off" in preferences and then starting a print. Just tried it on my own machine.

Edited March 29, 2017 by Guest

[SyntaxTerror 344]

Aaand then I realised I forgot about the second part of your question.

Right. I'm assuming for now that we're talking about some sort of relatively high powered LED here?

The main board has quite a few spare outputs that we can play with - but the thing is that they're unbuffered, direct from the microcontroller. The ATMEGA2560 can only source 40mA on a given output (and that's an absolute maximum rating so you need to stay well clear of it). Which I'm guessing is not enough to power your LED. I'm betting you'll need to buffer the output with a transistor or similar current source. Don't let that scare you though.

[umnbioprinting 2]

Good to hear that you've made progress! And not to worry - we're patient people. Just curious ones as well

For comparison purposes - which firmware version is your UM2 running?

Edit: I can confirm that at least with Tinker firmware, the LEDs do not turn on when set to "always off" in preferences and then starting a print. Just tried it on my own machine.

 

Thanks for your patience! I just sent you a message with some pics. I have the most current version of [what I assume is] the official Ultimaker firmware. I just installed it recently through Cura (usb connected). Haven't really looked into Tinker firmware before, but I just looked it up, and I think I'm already sold! I'm going to install it tomorrow and give it a shot!

[umnbioprinting 2]

Aaand then I realised I forgot about the second part of your question.

Right. I'm assuming for now that we're talking about some sort of relatively high powered LED here?

The main board has quite a few spare outputs that we can play with - but the thing is that they're unbuffered, direct from the microcontroller. The ATMEGA2560 can only source 40mA on a given output (and that's an absolute maximum rating so you need to stay well clear of it). Which I'm guessing is not enough to power your LED. I'm betting you'll need to buffer the output with a transistor or similar current source. Don't let that scare you though.

 

The LEDs on the commercial bioprinters in our lab are 3.5V, 0.5A, so I just bought a handful of those. I think one will do, honestly. Regardless, it sounds like that's still too much power for the microcontroller. It looks like I have a little research to do, but don't worry, I'm not going to come this far and back out! I'll persevere! Thank you, once again, for your help!

[SyntaxTerror 344]

The LEDs on the commercial bioprinters in our lab are 3.5V, 0.5A, so I just bought a handful of those.  I think one will do, honestly.  Regardless, it sounds like that's still too much power for the microcontroller.  It looks like I have a little research to do, but don't worry, I'm not going to come this far and back out!  I'll persevere! Thank you, once again, for your help!

 

Yeah, a half ampere is far beyond what the microcontroller can deliver. But as you've got a laboratory power supply already sitting there for the 12V supply, it's really just a matter of:

 

• Finding a series resistor for the LED

• Finding a suitable switching transistor

• Picking a control line from the EXT connectors

• Using the M42 command - this time with a pin argument (as otherwise it defaults to controlling the LED pin) - to control the switching transistor

 

If the diodes are 3.5V, 500mA (assuming you'll be using a single LED) and your supply is set to 12V, that means we'll want 8.5V across the limiting resistor. 8.5V / 0.5A = 17 ohms. The nearest E12 resistor value is 18 ohms which is close enough for rock and roll. It'll need to be able to handle some wattage though, as we're going to burn over 4W in it this way. That's of course just one example, using a single diode. We can modify things according to your grand master plan.

Edited March 30, 2017 by Guest

[umnbioprinting 2]

I'm looking into this option today! About to install Tinkerware and test the extrusion! Thanks again!

[Melka 57]

I think some guys in this topic should be included as authors in your article as they significantly contributed to the project.

Where do you plan to submit ?

[umnbioprinting 2]

I think some guys in this topic should be included as authors in your article as they significantly contributed to the project.

Where do you plan to submit ?

 

I agree! Don't worry, I will be private messaging them to discuss just that eventually. We're still in the early stages. I haven't done anything besides get it working and test cell viability in one test print. We still need to run an actual project through it, and I'm not there yet.

[Melka 57]

Super cool, let's go for Cell