I've finally got the test bench setup for the FoT MGFR pump with the 4mm gear set (FG204).

Here is a picture of the test bench:

From the output port of the pump is a check valve, then an OPV, then a pressure transducer, then a needle valve to simulate the puck's back pressure.

I've used an Arduino Nano for both monitoring the test bench's motor voltage and pressure transducer readings, as well as controlling the pump's 0-5V speed input. I'm interfacing with the Arduino over Serial Bluetooth in order to plot the pressure readings and control the pump via an app I wrote on an Android Nexus 7 tablet.

The screen recording includes audio so you can hear the pump. I've got some leaking when I applied pressure on the needle valve but I hope to tighten things up and retest tomorrow with pressure.

Here we go with a real pressure test! I did a picture-in-picture thing so you can see when I close and open the needle valve. I close it all the way to act like a blind filter. I'm glad that the pressure transducer seems to be working as expected. The OPV is set to the 125 psi mark.

Looks almost like a piston profile... Very impressive setup, Matt!

How predictable/controllable is the flow rate while subject to an unknown and changing resistance?

Very nice setup and tests, congrats!

I'm using it with a Bezzera BZ09 and Arduino, but I got a chep pressure sensor from eBay. It's reasonable, but I have to do an average of readings for a more stable value. I did all the things I wanted, bluetooth to setup alarm and group and boiler temp, but we're using it (at work) only manually controlled yet, and as I have no LCD display - the feedback is the pressure gauge...

I did a fun thing too: a very crude model to use the speedometer (from the pump), pressure reading and motor input setting (that gives me a maximum pressure estimate if flow would be zero) to calculate flow. The error is not so small (maybe around 10%), but I use this to turn the heat element of the boiler proportionaly to flow during the shot and it works great - I spare the PID of big changes of the system temperature (the boiler is small, 500ml).

Márcio.

Hi Márcio,

Your flow estimation technique sounds really interesting. How do you calculate it? So you're using the 4mm gear set and not the 9mm? I'm interested in testing the 9mm next to check for noise reduction.

This is pressure transducer I'm using
http://www.ebay.com/itm/181138034634?ss ... 1497.l2649
maybe it is similar to yours. I might be adding a manual gauge to verify the readings.

Matt

I'll take a look at the code to make sure before I tell you.

I'm using the 4mm. Shawn, from FOT, told me this about the FG100 and its 9mm gears:

"So they can barely reach 9 bar (130 psi) if pulling from an atmospheric pressure reservoir. If you want it to work reliably to 9 bar at the outlet then you would definitely need some decent inlet pressure in order to reduce the load on the motor."

But if someone could test it, it would be great.

I've mailed my pump back to Shawn who will be switching out the gears for the 9mm set which I will be testing on my rig as soon as I get it back. I asked him why there isn't a 7 or 8mm set; something that would be a nice compromise between noise and reaching the required pressure whether from a reservoir or plumbed in but he says they have no plans to develop such a thing since their 4 and 9 gearsets are meeting their customers' requirements just fine. Oh well.

Here is a video with sound checking out the sound levels from the 9mm gearset version.