Arduino Project: HLT volume display using bathroom scales

[Andy]

Can you not buy a pressure sensor as a discrete component and build it into a baseplate of some kind?

I could Jim but bathroom scales already have all that and are cheap (cheaper than the pressure sensor would cost).

[roscoe]

I think load cells / scales are the way to go, although a sight glass is easier for HLT !
I also thought of the arduino solution and will follow your progress with interest. I have a £50 fancy pants scale under my mash tun with bright display which I find is great, accurate and saves any pre-weigh mess, confusion and time (it also gets used for no brewing things as well)

[wmk]

[quote="Fil"]nice one wmk

as an arduino novice trying to learn, can i ask why you selected the lm35 probes, was it just a case of having them? most arduino beer temperature projects ive come accross seem to use the DS18B20 1 wire sensors.[/quote]

Yeah simply a case of what I had on hand (lm60). I'd prefer the ds18b20 in the final setup as you can have long wires between the adc and the temperature sensor (as it does the temperature conversion before sending you the digital data). Also you can get them off ebay in fully made up probes for fairly cheap.

All my brewing and arduino design choices are simply what I had available the GSM shield is only there because it was jammed so tight that I was worried about breaking the pins if I pulled it off. Also it cost me nearly £50 and I'll be dammed if I don't some how involve it in every project I ever do to justify the cost.

[Fil]

Ahh i was just stunned with the apparent speed your solution was created in, seemed like it was a sidethought during typing the post..

im working slowly on an arduino brew controller and wondered if your choice was based on it being a better tool for the job ..

[Andy]

The project is rebooted!





£7.99 digital scales from Lidl

[Andy]

Had a closer look at the PCB and the load cells.

There are four load cells, one in each corner of the scale. Each load cell has three wires, red, blue and white.

For each pair of load cells (the two left hand cells make one pair, the right hand cells make the other pair) then the red wires are connected together on the PCB.

The left hand white wires go to E+ and S- (excite and sense - excite is the input voltage and sense is the voltage to read).
The blue wires are connected on the PCB with the blue wire diagonally opposite.
The right hand white wires go to E- and S+.

The resistance between blue and white, white and red for each load cell at rest is about 870 ohm.

[Andy]

So my plan is to remove all the wires from the PCB and connect the red pairs together as they are on the PCB, likewise for the blue wires (diagonally opposite). Then I'd apply power to the E+ and E- white wires and use an amplifier to boost the S+, S- voltage with the boosted signal connected to the Arduino analogue input.

[kinnockthecat]

Look forward to seeing the results!

[Andy]

Would be a good upgrade for the Flying Goose also

[dean_wales]

You see - all you needed was a kick up the arse!

Watching with great intrest. BTW have you thought about the damage over time to the cells if left under vessels due to constant weight? Or are you going to remove them between brews?

Dean.

[Andy]

I've got the extra bits and pieces I need (breadboard, INA125P amplifier, OLED display) currently on their way so hopefully more progress soon!

I hadn't thought about the load on the cells, but when not in use the empty HLT weighs about 4kg so don't see a problem leaving it all in situ.

I took inspiration from this project -> http://www.deferredprocrastination.co.u ... h-arduino/

So much good information there and pretty similar to what I'm doing.

[Jim]

Great work so far Andy! I love this kind of mucking about with stuff.

[Andy]

All the "bits" have arrived, just need assembling and some code writing now

[JabbA]

How 's it coming along Andy? I had the very same idea as part of the gradual upgrade of my Arduino HERMS setup and the load cells have finally arrived from China!

This is as far as I've gotten so far


The INA125 chip came curtsey of Texas Instrument's generous free sample policy and I've also got a cheep solenoid valve off of EBay to control the flow from the HLT. The problem is the valve needs quite a bit of pressure behind it, a quick test last night resulted in a drip every few seconds but I'm sure I can live with that.

Cheers,
Jamie

[Fil]

is http://www.ebay.com/itm/HX711-Weighing- ... 27ef17b84c any use/interest for this project?