Tag Archives: micro-fit-3.0

Coffee boss day 10 – Neat board and RFID

Been a while! Coffee boss has a great upgrade recently, that’s the current sensor. This, combined with a new firmware that counts the time since the last time the current went low (so signifying that a boil cycle has completed therefore a new pot is ready) means that this is suddenly actually useful.

Pictured here is the various circuits combined on one piece of board. The back is a bit of a rats-nest but this should all fit in a project box reasonably neatly. I’ve made up a power cable with twisted mains cable where the individual conductors can be separated out without having to cut any insulation but I need to get that cleared off with the estates people – I would still prefer a sealed moulded plug on the part that plugs into the coffee machine itself.

The reason why I put the current sensor on this part (near the machine, where there water is) is because the other option is down on the floor, and the wire going to the sensor isn’t very long. That’s still a decent option for a more permanent installation.

Next to it is a new RFID reader, a board made by Elechouse based on a PN532 chip. This is a neat little beast but I’ve had a right battle getting it working. Elechouse have some libraries for Arduino but there are some improved ones here:

This module has a serial, an SPI and an I2C interface, with a little set of dip switches to control which one to use. I tried all kinds of ways and could. not. get. it. working. on the ESP32, only to have it work first time with a regular ATMEGA based Arduino board. Something about the ESP32 perhaps? My circuit? Likely.

Cut a long story short, I have to do a full power cycle of the ESP32 to get the PN532 to initialise properly. Reset won’t do it – presume the reset button only resets the microcontroller rather than actually interrupts the power – and that makes a difference.

Only just got this working this evening, and made up some neat cables. I’ll take it for a test drive tomorrow.

What’s the RFID reader for?

Oh right, yes, it’s so that coffee drinkers can bump their work ID when they have a cup of coffee and the machine will repeat back how many cups they’ve had recently. It’s so they can think about how much they owe. It won’t ever know who they are, but the cards that our IDs are printed onto have unique identifiers so can track you across sessions.

The Connectors Saga

  1. I decided to use Molex Mini-fit jr sockets on this because I had a few sets left-over from Polargraph drawing machines. I never actually used them on the Polargraph and they’ve been burning a hole in my pocket ever since since they are so adorable.
  2. I dismantled the Coffee Boss machine and stripped down the cable ends… And realised that the metal crimp contacts I had to go into the Mini-fit jr plugs were the wrong kind! I’ve got a reel of contacts for “Microlock Plus” system. As soon as I noticed, I remembered kicking myself for making that mistake the first time around. At least one reason why I never used these plugs and sockets.
  3. I ordered some crimp contacts for Mini-fit jr, along with a couple of sets of backshells for the plugs, so they look super pro. Expensive! But worth is for the pro-ness.
  4. When they arrived after the weekend, I crimped a couple onto the current sensor… And realised they wouldn’t fit into the plugs I had. I hadn’t wanted to test it before crimping them in case they got stuck in the plug and I couldn’t get them out.
  5. I realised that my plugs and sockets weren’t Mini-fit jr at all… They were Micro-fit 3.0.
  6. Always had been Micro-fit 3.0.
  7. And a cursory glance at the bags they were stored in confirmed that.
  8. So I ordered some crimp contacts for Micro-fit 3.0. Got them, fitted them tonight, and now we’re cooking.
  9. I wish there were some backshells to be had for the Micro-fit system, they are super pro.