Scale Design Progress (DIY with your DIY update)

submitted almost 10 years ago by queuetueProud Sidebar Reader!

Some of you were interested in the progress, others wanted to see the code and specs.

Some people offered money to help offset costs of the project, and to get one built and programmed - if you were serious, PM me and I'll send you my paypal info. I need to stress this is not a finished product, the cost is not finalized, and it'll take a while to complete.

Status

http://imgur.com/aW5TMOA

Going well, the scale hardware is essentially working and complete. There are noise issues I'm tracking down which will require a better (slightly more expensive) load sensor or a better shield for the ADC.

It seemed fruitless to order those parts now (Christmas), so I'm working with what I've got at the moment, and getting 0.01g accuracy at 5Kg with about .02 g of noise.

Technical Stuff

Here's a diagram of the components I'm using now: Arduino Nano, HX711 ADC, Adafruit HT16K3 7-segment display and an HM-10 BLE module.

https://imgur.com/aGo3kkY

I've created two Arduino libraries to help the process, they have been submitted and will hopefully soon become official libraries included with the Arduino IDE.

HX711 Driver

Balance Library

Sample code is included with both libraries.

EDIT: For those playing along at home, the block diagram is wrong. The HM10 is a 3.3v circuit, that green line should be connected to the 3.3v voltage (pin2) not the 5v. Following the circuit above this will fry your bluetooth module.

Comments

2 points

by Eizoozalmost 10 years agoProud Sidebar Reader!

When this is done how much will I be able to buy one for?

2 points

by tranceinatealmost 10 years agoMixologist

> the cost is not finalized, and it'll take a while to complete.

2 points

by NotCharlesMansonalmost 10 years ago

1,000 units? I'll take two.

2 points

by tranceinatealmost 10 years agoMixologist

I'd take 1,000 of your units, bebecakes c;

1 points

by Eizoozalmost 10 years agoProud Sidebar Reader!

I'm awesome at not reading carefully. Thanks for the reminder.

1 points

by PierGarrettinnialmost 10 years ago

Thanks for the status update, this is great news. Hows the noise at under 1Kg?

1 points

by queuetuealmost 10 years agoProud Sidebar Reader!

By @5k, I'm not referencing the measurement level, but the capacity (as limited by the load cell in the system.)

Voltage from lower-capacity load cells (100g, 500g) have greater voltage differentials between "grams" and are easier to reduce noise with.

So, with this 5kg load cell, I get about .02g of noise "jitter" no matter what the measurement is - this is simplified, so if you want more details, I can describe the multi-step calibration window functionality I've built in.

With a lower-rated load cell, I could probably reduce the noise considerably.

1 points

by PierGarrettinnialmost 10 years ago

This explanation cleared it up for me, thanks.

1 points

by grrumble66almost 10 years ago

If I'm understanding this correctly, the ability to mix up a gallon of eliquid comes with ~1 drop jitter as a downside?

Sounds like a success to me. :P

1 points

by queuetuealmost 10 years agoProud Sidebar Reader!

That does seem to be accurate, although I'd need better calibration weights to test it.

Unfortunately, it also means 1mg of flavor for a 10mg mix also comes with ~.02mg of jitter, which makes it unusable for small batches.

1 points

by o0turdburglar0oalmost 10 years ago

This is awesome.

Are you planning on selling some of these, or just providing the OS details so people can DIY?

Also, is there a chance of getting a version sans-bluetooth? How much of the current cost is attributed to the BT board?

-5 points

by DIY_EjuiceTron5000almost 10 years agoOne of "The Damned"

To make my job easier when I'm launched, please get in the habit of flairing your posts. If you can't find a flair that applies, please let /u/skiddlzninja know so it can be remedied. Thank you.

1 points

by queuetuealmost 10 years agoProud Sidebar Reader!

Ok, I hope this isn't the direction of things to come. This sucks. /u/skiddlzninja, is this going to really happen in every post?

0 points

by skiddlzninjaalmost 10 years agoThat one moderator. You know, the honey guy.

For a month, it will post on every thread that doesn't have flair in order to get everyone into the habit of putting flair on their submissions. Not only for the bot, but to make searching easier in the future.