emonTX V4 Pre Purchase Questions

Hi All

First of all, thanks for creating some great products. I built a EVSE last year, and it’s been running well.

I’m looking on expanding the system, and I’ve a couple of questions before I place an order for some gear.

  1. I understand that the emonTX V4 will have an additional 6 Chanel expansion board. Is it possible to order the expansion board and wait for the firmware to be ready? (Want to save on freight, as it’s expensive to ship 1/2 across the globe.)
  2. Is there a difference between a normal Pi and a emon Base when using direct USB connection and no a RF connection?
  3. Is there anything stopping me from putting multiple turns through the CT. I have some circuits that only have about 5A max going through, so contemplating increasing the accuracy of the monitoring this way.
  4. I’m thinking of using the emonTX V4 to do some basic monitoring of my HWHP. With the recent posts about temp monitoring and CT reading will this be an issue with the 6 channel expansion board, or is it better to offload this work to the Pi from the get go?

Thanks again


  1. The library you need plus examples sketches was published yesterday. But the expansion board itself isn’t available in quantities yet.
  2. Not as far as I know.
  3. Not at all - this is how I get 250 A to test the c.t. (from a 6.5 V, 8 A transformer). The only constraint is the wire size and the c.t’s aperture.
  4. Yes, I’m afraid so. The temperature measurement takes far too much time (to fetch the values via the One-wire bus) so it’s not been possible to have temperatures - as explained elsewhere. It will be far better to leave the temperature measurement to the Pi.

Any indication as to when the expansion board will be available?

Best email The Shop for this. I have a pre-production one (for obvious reasons). I’m not involved with organising the manufacture, but I think it’s simply a case of getting a batch made - plus of course the replacement front panel.

Thanks. I’ve got in touch with the sales team, and will take it from there.

Hello Neil, thanks for your email. For anyone else interested, I will likely have a small number of the expansion boards ready in a couple of weeks, waiting on one set of components to come from the US. The fascia will likely be a bit longer. I think it will be around 3 weeks time until both the expansion boards and fascias are in stock.