Hi @CamDavidsonPilon! Martin told us (AMYBO HMC Clinic team) about the pinch valve you got working and suggested we reach out to you for specifics about how you set it up and documentation for your pinch valve. The medical grade one we have (link below) is not strong enough to pinch the non-CO2 permeable tubing, and neither is our current design. We are working on a mechanical advantage system that will amplify the force, but were wondering if you have any other suggestions based on your experiments.
Hi @arlombardo, are you using a 12V power supply in the barrel connector on the HAT? Can you link to the tubing you are using, too?
Hi Cam
@gendor mentioned that @arlombardo hadn’t gotten back to you on this. They’ve been making amazing progress since I recommended they get in touch, but are now working all hours on their final experiments, poster & presentation. So I thought I should step in to give you some context.
I don’t think they had reached the point of hooking it up to the Pioreactor at the time of your response, so it was just being tested with a bench power supply. But yes the standard electroPioreactor uses the 12V power supply in the barrel connector on the HAT - so that would have been the eventual aim, once they got their pinch valve design working.
While I have seen videos of their using what I believe is 3/16" ID PU tubing which I understand they previously recorded as requiring 10N to pinch, they are now recording ~80N required to pinch it. If it is the same tubing that I have, I wouldn’t expect it to be pinchable with a 12V solenoid let alone the 5V we were hoping for. I am however told that, while the video recording failed, they also tried with the stock silicone tubing that comes with the Pioreactor & bubbles were still passing despite their using the strongest spring that the solenoid could pull back. This had me really confused which is why I suggested they check to see if you had to do anything special to for your pinch valve experiments to work.
Since then they have reported that by adding a carbon fibre reinforced lever, they are getting more than enough force to pinch the tubing, it’s giving so much force that they’re having to reinforce the plate that’s holding the tubing in place.
I’ll ask them to triple check that their original design was unable to pinch the stock Pioreactor 1/16" ID silicone tubing.
Either way, we’ll hopefully soon be able to post their design to OpenValve.org
Hi @CamDavidsonPilon apologies for the delay in responding. It has been a crazy week. We are not yet using the Pioreactor as a power source, but have confirmed that it will work for powering the solenoid as it is drawing well under 5A (we got a 5A power converter rather than a 3A). The tubing is from our stockroom, I am not sure what kind it is. I will source some of the pioreactor tubing today and will hopefully have that fully tested by the time we need to have our poster submitted. If not, we will do theoretical calculations to anticipate if it will be able to prevent CO2 flow. We will have our design posted to printables (and linked here and in the AMYBO forum) by tomorrow night.
The experiments we did used a previous (no-name) silicone tubing, which made have had a smaller durometer than what we ship now. However, even our tubing now is quite soft (the tubing we currently ship has low gas permeability btw).
It sounds like you got it working now though?
The pinch valves we tested with are from here