Vacuum Pump Control

[Mick Tomlin]

During the first lockdown I read an article on building a digital control vacuum gauge and pump switch.

https://www.rcgroups.com/forums/showthr ... uge-Switch

So having some time on my hands I decided to build one.
Other than wiring multi wing servos this was my first attempt at constructing electronic gadgetry.
It has been used to vacuum bag some 2mt wing panels.
Set at 15inHg max with 13inHg low settings the pump ran 4 times for total of 27 second during a 12 hour cure.
Attached are some pictures of the setup.
It is compact, quiet in operation and did not cost a lot to build.
Definitely worth considering if you are into vacuum bagging.
Mick

[paulj]

That looks great Mick!

[Mick Tomlin]

Thanks Paul
It works very well and the vac control has to be seen.
Get the bag sealed and it hardly runs tops up at all.
Ideal for me as I use a spare bedroom for building and have to keep noise under control.
Where it would be a great help is if you use a pump that emits an oil mist as this set up runs so infrequently it would reduce that to an absolute minimum.
Not that expensive to construct either and the build guide is superb, I did it as my first electronic build.

Mick

[Peter Balcombe]

The linked RC Groups thread also has a 20x4 LCD option which I have looked at as this is able to display all data in just 3 screens rather than many more.
As the available firmware uses nearly all available program & memory resources, plus the need to have 2 twiddle pots for vacuum threshold/switching margin inputs, I have also tweaked the firmware to allow the user to compile a single vacuum measurement unit (mBar, mmHg, inHg) rather than select any one at any time, plus replaced the 2 pots with a single rotary encoder switch to toggle between Threshold/Margin value selection.
The compiled code now only uses about 50% of the Arduino resources, so should be more stable.
I’m just about to start packaging the controller into a plastic box, together with 12v psu, sensor & 2 relays. Hopefully it will all fit.

[Mick Tomlin]

Peter
That looks very good indeed and your idea of getting more info shown is excellent.
How long have you been working on the controller and would you be prepared to share the upgrades that you have made.

Regards Mick

[Peter Balcombe]

Hi Mick,
The displays are basically exactly what you should get with the 20x4 display version of the latest software version (there is both a 16x2 & 20x4 version of the software - look for version 4.0.0 in the latest page or so of posts, so it may be worth you looking at the 16x2 display version of that if not already there.
I think the 16x2 version can display similar data to the 20x4, but obviously has to cycle through more display screens to show it all.
The original program is very versatile & I think it allows you to even choose what data to put on which screen ‘page’.
In fact I thought the original program to be a little too versatile, making the program overweight. For instance, I thought that users would have a favourite pressure value unit & always stick to that in practice.
You mentioned inHg in your post, but I would probably always use mBar.

I only picked up on the controller program last weekend & once I quickly had it running on an Arduino Uno & I2C 20x4 display that I had lying around, I decided to try replacing to 2 pots - but needed more processor resources, hence first slimming down by compiling for only one measurement unit.
I had used the encoder method of input before on a much simpler controller.

I am more than happy to share my updated versions, noting that they are currently only for the 20x4 display - although it’s probably not a big job to tweak the 16x2 version as well if needed.
The way the program is written, I think only the display.info file would need to be changed from my encoder version apart from redefining the display setup in the LCD setup part of the main sketch.
Peter

[Peter Balcombe]

Mick,
Did you use std. 4” PVC soil pipe & end caps for your large reservoirs?
What did you use for the smaller one (2”)?
It looks as if you have your smaller reservoir on the pump side of the check valve & a solenoid operated dump port with silencer fitted. Is that correct?
Thus it appears that you open the solenoid dump valve to remove any load on the pump when it starts, then close the solenoid valve & pull vacuum on small reservoir before check valve opens to pull on the rest of the system?

Mick, I assume that you are using an I2C display rather than a parallel interface type. I have seen a schematic for parallel but the firmware all seems to be for I2C.
Peter

[Mick Tomlin]

Hi Peter
My using Hg readings probably gives my age away.
Having thought about changing the display I think I will stay with what I have.
My build was not without some frustration with the controller, about a week to fathom out how to get the display to work.
Once that was sorted all worked and is still working very well so best to leave well enough alone.
Your upgrade to the firmware could well be of benefit to others that may build one.
The pipe that I used is solid wall soil pipe with suitable end caps.
The reservoir consists of 2 x 100mm x 300mm pipes and the relief tank 200mm x 1.5 in. waste pipe, all fitted and sealed with suitable end caps.
All of the metal fittings were BSP, the only problem that I had with the plumbing was getting an airtight seal on the thru tank fittings. This I cured with two hydraulic sealing washers with a slimmed down nut locking them on the inside of the end caps.
I had a Thomas pump in the corner and used that. The analogue gauge was lying around so incorporated that as a reference guide to the display.
The pump is rated to 21Hg and as set up I have bagged 2mt wing panels with ease set at 16Hg high and 14Hg low.
The unit is leak free, getting the bag leak free is the frustrating part.
The vacuum pressure release is necessary if you do not want to stall the pump on restart. Was part of my learning curve.

Hope that helps
Mick

[Peter Balcombe]

Thanks for the info Mick.
I2C displays sourced from different suppliers can use various I2C addresses (e.g. mine uses 0x27 instead of the 0x38 used in the default sketch).
However, a device address is easily found by loading a sketch called I2C scanner which lists (on the PC screen by selecting the serial terminal display, with the correct baud rate) the addresses of every device found on the I2C highway.

There are also different LCD I2C libraries out there, but using the specified one should work ok straight away if the I2C address is correct.
It appears that you can get more display screens up by cycling through them with quick clicks on the pushbutton - at least on the later posted version of the firmware.

Peter

[Mick Tomlin]

Peter
The address was my problem.
Got there in the end and learnt a lot. The plumbing was the easy part, my computer experience extends to turning them on and off.
Let us know how you get on and what your impression is when you have finished.
Mick