I would like to build my own emontx4 board from the Eagle sch/brd files on Github. However, not all the parts are annotated (e.g. R5 and many others have no value). Also, no required power or tolerances are given for any of the resistors. I can conservatively guess the power from the footprint, but the tolerance is hard to gauge.
Is there a BOM anywhere that lists the recommended parts?
Welcome, Jon, to the OEM forum.
The short answer is no, I don’t know of a complete version. Only a few components are critical with regards to accuracy, and I could probably find this if I looked at the discussions we had early on in the design stage - but it would take a while. @glyn.hudson or @TrystanLea should have the full list to hand.
@Robert.Wall - Thanks for replying.
Related to my question, I can also see that R5 and R7 (and related resistors on the other CT inputs) appear to be mutually exclusive options for the same functional part (SMD or THT options). Please can you confirm that this is the case, and I should fit one, or the other, not both.
What appear to be burden resistors are in fact placeholders for either a SMT or a wire-ended component, should you be using a c.t. without the internal burden. The 0.333 V voltage-output c.t’s we recommend (and stock in The Shop) have an internal burden, so do not require a second.
If you use a ‘pure’ c.t., then you need a burden to give 0.333 V rms at rated (or your design maximum) current.
As Robert said, you do not need to fit those burden resistors if your using voltage output CT sensors such as those that we supply with the EmonTx4 in the shop. We do not populate the parts that have no value (I think it’s only those burden resistor options).
Do you intend to publish the full BOM?
I guess it hadn’t really crossed my mind, thinking you can export the BOM from the eagle files, but then that does miss the tolerance info… Im sure we could publish it
Is there a specific bill of materials?
I’d point out to everyone trying to build their own emonTx that it’s profits from the sales in the OEM shop that pay for the designers, all the development work and this website. Without all of that, there would be no emonTx4 to copy.
A full BOM would be awesome, or just a list of the passives with tolerance and ideally power (not critical, as mentioned before).
@Robert.Wall - Yes, that’s a fair point. But I would like to tweak it for my installation, which requires 10 CT’s, and would prefer a single board, insted of using the extender. I also just enjoy the process of making my own - In truth, it’s more about the journey than the final result, and as a hobbyist, I learn something from each build I do.
Off topic for this thread, but have you considered a mechanism for inviting donations, to complement the shop revenue?
Thanks @jrbloom, I’ve uploaded the BOM alonside the hardware files here: emontx4/hardware/v4.0.5 at main · openenergymonitor/emontx4 · GitHub
Thanks for the thought! we haven’t got anything set up for this yet but it’s a good idea!