Cheap Vacuum Control Solutions

[Thetetraguy]

I was curious if anyone had a cheap (under $500) option to assist in automating the rotovape.
Only ones i find easily marketed is around 1,300 and that seems rediculous when its just a digital vacuum gauge, SSRelay, dials and some computer logic.
I tried wiring my own but cant get my ADS to read a proper voltage from the Digital Vacuum Guage, so i gave up on that and looking for something under $500

[GroovyOctopusLabs]

Budget Digital Vacuum Sensor, read a 60$ pirani gauge through your PC

In the hunt for a reasonable budget vacuum gauge @JacobsLadder was kind enough to mention the MKS 901p sensor and provide some information to help me get it working properly. This gauge can be easily purchased on ebay for quite cheap, around 55$ shipped. The transducer easily communicates over serial port to a PC. This requires 2 wires for serial communication, and a separate power supply that ranges from 9vdc to 30vdc. You want to choose a power supply with a very low power output. I searc…

Might help

[Speedofgreen]

Are you trying to break vacuum to drain vessels automatically? Or you just want to control the vac depth?

[Thetetraguy]

Vac depth

[Roguelab]

Manual vac valve and a micron meter on a separate hose so once set don t touch

[Lewis_Bronsted]

I just went to the ancient four letter auction site and searched for “buchi vacuum controller” and some pre owned units are in/close to your stated cost, here at least, some of the same ones are way way more. If you hunt a bit deals can be found. Near gear is nice, but often used gear is worth considering

[Thetetraguy]

Ty, im going to go with both solutions, the used buchi and try and configure a 901p sensor. Thank you guys for the help

[QGA]

I cant tell what you want really. Something to read for pressure levels to you or a way to control the vacuum levels or both?

[Thetetraguy]

I wanted to keep a specified vaccuum depth over long periods of time with varying loads

[QGA]

I am not sure what loads mean but in my academic lab I use an old manometer mercury vacuum gauge that is pretty low tech and a old bunsen burner needle valve to bleed in air to control vacuum levels.

[Thetetraguy]

What i meant about varying loads, is that there might be alot of solvent evaporating or there might be very little but regardless i want it at a specific vaccumm level automatically without me adjusting anything

[QGA]

figure out how to make your own manometer with mercury and manostat with an adjustable needle valve.

Its a vacuum gauge it gives you the read out vapor pressure within your system, so it will give you a readout regardless of the load.

[Thetetraguy]

Im not looking for just a readout, my current setup is pump → needle valve → guage → cold trap → rotovape.
I dont want the pump sucking more than it needs to, so when there is nothing in the flask, the needle valve setup allows it to surpass the vaccum level i want. Then when different amount of liquid gets injected into the roto, the vaccumm level changes. Hopefully i can set up solenoid valves and relays to turn on the pump when needed and open the valves when needed

[vdWcontact]

You want the Buchi controller. I used one for years in grad school. You can set it to a specified depth, start vacuum, and walk away knowing it won’t pull below your specified depth. Or you can manually adjust the depth until you have a good evaporation rate and walk away.

They do seem to be really expensive for what they are, but I don’t have experience with any other automatic controller so I can’t recommend anything else. Heidolph probably makes a similar device.

EDIT: Forgot to say this but make sure your pump is compatible with the controller. The controller I used clicked the pump on and off as needed to maintain vac depth. It’s possible that non-buchi diaphragm pumps don’t have the necessary connections for this type of control.