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asbach

Printable Peristaltic Pump

by asbach May 19, 2011
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have you let the pump sit in a vertical orientation to see how much if any liquid flows bank into the source over time?

What are the OD and ID specs for the ball bearing you used here?

how much l/minute does is pump, and at how many psi / bar?

Awesome idea using the two smaller hubs to support the tubing and extend the tubing life!

Almost excactly what I was looking for. Thanks for the files. Could you tell more about fans and how you control and monitor them? I'd like to connect the monitoring a the fan speed to a raspberry pi.
Do you happen to know where I could find ressources on how to use computer fans in a project ?
I'd love to be able to modify the speed of it (which I guess could be done by regulating the intensity of the electric current provided to it...#hoping #searching.

Most computer fans have 3 wires coming out. One is a ground wire, one is a power wire, and one is a sense wire. The sense wire outputs a certain amount of pulses per revolution (2 is typical) that you can measure with a microcontroller (like the Raspberry Pi) using a digital input pin. The sense wire can also be called a tach wire (tachometer). There are some computer fans that have 4 wires... the 4th is for controlling the speed.
To control the fan speed for both 3 and 4-pin fans, you would use pulse width modulation (PWM). The R-Pi can create a PWM signal on one of its digital output pins. Here is a link explaining PWM:
http://www.embedded.com/electronics-blogs/beginner-s-corner/4023833/Introduction-to-Pulse-Width-Modulationhttp://www.embedded.com/electr...
For the 4-pin fans, you can just supply PWM directly into the control pin. Can somebody double check me on that, because I'm not sure if a 3.3v PWM from the R-Pi has high enough voltage for 5v/12v fan's onboard speed controller.
For 3-pin fans, you would have to use PWM on the power wire. However, you can't connect the PWM signal from the R-Pi directly to the power wire of the fan because 1: CPU fans don't operate on 3.3V and 2: The R-Pi digital output pins can't supply enough current to power the fan. So you will have to feed the PWM from the R-Pi into a transistor that is connected to both the fan and a strong enough voltage source. I googled around, and this gives a good example of how to use the transistor:
http://www.techpowerup.com/forums/threads/so-you-want-pwm-control-of-your-new-cpu-fan.107135/http://www.techpowerup.com/for...
You will have to do some calculations to get your transistor set up correctly, but it's not too hard. Try the concept out with an LED first, that way you don't fry your fan while you are learning :)
Once you have PWM set up, you can create a feedback loop that accurately controls the fan speed. Your R-Pi will continuously measure the actual fan speed using the fan's sense/tach pin, and then the R-Pi will continuously adjust the PWM duty cycle to make sure the fan's actual speed meets the desired speed. You can use a PID controller for this... here is a link explaining PID:
http://www.csimn.com/CSI_pages/PIDforDummies.htmlhttp://www.csimn.com/CSI_pages...
For starters, you can just trying a P controller and adjust the gain Kp:
PWMDutyCycle = (DesiredFanSpeed - ActualFanSpeed)*Kp

stepper motor would be great for this (and would most likely have enough torque on a nema 17 or larger stepper to run the pump without gearing it)

Do you think that a tourniquet would do the trick? I hope that's the right transation for the tubing that's used for blood withdrawing.

I used the pump in a 3D printing / rapid prototyping demo that I gave to a group of high school students. It worked well, and they all seemed to enjoyed it. You may have helped inspire a few future engineers. Good design.

that would be useful to mine small rc submarine

great! i like the idea very much - keep us updated if it works with the silicon tubing!

Tube and the gear motor will arrive on wednesday.

did anyone try the lot of printed gear solutions with any success? i would love to make it all printable, but i have my doubts that the gears are strong enough - at least with the current tube - unfortunately i used my last ABS stock for the pump - but there are 6kg of ABS on it's way.

hm...replacing the Pump Wheels with ball bearings should yield even better results...

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gt; http://www.thingiverse.com/thing:4312http://www.thingiverse.com/thi...

Ball Bearing

thanks for the advise, i thought about it but i have to admit i didn't have any at hand. After disassembling even a printer i ended up with no bearings bigger than those in the pc fans. so i went for a shot with the things i had available. The steel rods made from the rivets and the ABS combine really well and seem to add marginally to the torque requirements - i didn't expect this - but hey if it works with the better silicone tube all is well, it is really simple and if you need a all-fluid pump you can built one in less than 2 hours.

Why bearings?

If his motor is sized for proper torque and his rollers roll. why bother with complication, weight, parts, expense. This is a very simple eloquent design. The pump only needs to apply consistent even pressure along a length of tube - intermittently and to allow more fluids to enter for the transfe
r to the exit of the pump. This type of pump is not fast for high capacity. So, not much heat or friction. Just an even easy rotation. Right?

This is truly amazing. Was this done in TinkerCAD?

yes it was made completely in tinkercad - i have to admit that it is really great for simple things - i did it from scratch in about 3-4 hours (with 3 or 4 iterations) - i even skipped any tutorials, so i do not know any hidden features of it yet. There is a way to share the project urls for others to tinker along, but that i didn't figure out yet, will post the links when i do ;)