Tipping the scales

I am getting really good at upgrading the scales to do WiFi now, and read cards. The card of choice is a Monzo card which works perfectly well as an ID for weighing yourself. Notably Amex have an ID of 00000000 which is useless.

Really neat PCB, locking molex connectors, cables, the lot. It is working well. Marsden kindly sent the service manual so I can set to "kg" and "st/lb" modes for those that like old-school weights.

The system has a QR code on the scales, which allows you to register any card against your email address. You then weigh yourself and tap the card on the scales to record the weight.

When you tap the card it beeps to confirm it is working, and keep beeping until a stable weight is recorded over WiFi to the server. Simple UI if ever I made one!

Sadly, I have fried a couple of boards whilst doing these upgrades, but Marsden do spare parts (not cheap) and whilst I have a few clues what I may have done, I am not 100% sure of how I killed them. I think, with care, and anti-static, and being neat (avoiding any shorts, or diodes backwards) I can do this reliably now. Obviously very unofficial so I cannot expect any help from Marsden. They do make very nice scales though.

The next challenge is to make the web site that holds the data have graphs and sharing options and so on. At present it is just a list of weights. But even that is working for relatives using this solution.

This is turning in to the new fat-shamers club or something, not sure.

But what was the first thing on the web site? after registering the domain? well, it was getting an excellent lawyer to put together the privacy policy for us and ensuring we are GDPR compliant.

You have to love any lawyer that covers standing on scales with your pet cat as part of the privacy policy. Thank you Neil.

Upgrading my Marsden M-125 scales to WiFi

I have some nice scales from Marsden, their M-125 column scales. I know they are not cheap (£235+VAT) but they are very good. If you are ordering for home you can ask them to allow stone/pounds as well as kg, which they seem happy to do. They work at 100g steps and can weight up to 250kg. What is nice is how consistent they are - none of this "best of three" effort on cheap bathroom scales.

But I wanted to get data out of them, and like proper scales they have a serial port (though it is a USB port). I was going to connect to a Raspberry Pi, and even have a Pi and a case, but I now realise I can WiFi connect them easily.

Using an ESP8266 in an ESP-01 package, I can receive the serial data and send over MQTT over WiFi, simple as that! It actually works out about half the cost of the USB cable alone - with the ESP-01 costing a whopping £2.75 from Amazon (more like 50p if you order from China).

It does involve adding a header to the main PCB, sadly (no doubt voiding any warranty). It would be nice if Marsden had a header on the board and did WiFi as an option. I am sure we (A&A) would be happy to provide some consultancy and custom firmware for such a project, just ask...

As for the software, well, I was actually able to use the Tasmota software as it will serial bridge to MQTT, but I then wrote my own (on GitHub). It sends via MQTT and/or via HTTP(s). It is a bit of a work in progress at the moment, but works well even so.

Here is how it is done...