EmonTx v2.5 and throughhole kits

2015-06-06 10:29:00 +00002015-06-06 10:29:00 +0000 Trystan Lea
three minutes reading time

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We've had quite a few people ask about the throughhole emontx v2 and emonGLCD's designs since we've moved away from stocking them in the shop and developed the pre assembled units. I've also had several conversations with people offline who said how much they enjoyed building the kits and encouraged us to keep supporting and stocking them. The challenge is the complexity of running an online shop with many different product lines and the additional workload of kiting and stock ordering - but it seems like it might be worthwhile for us to look into a way to make it possible.

The emontx v2 currently uses different 3.5mm jacks to the emontx v3 and emontx shield, It also required a different case which needed milling to use. To try and standardise on the components required I've been working on a new version that is designed to fit in the emonTH case that doesn't require milling and uses the higher quality 3.5mm jacks used on the emontx v3 and emontx shield.

As I got stuck in to the design I thought Id add the powering via AC circuitry that's on the emontx v3 and find a way of ensuring all spare IO is available + the addition of a row of terminal blocks with power, ADC's and digital IO breakout in much the same style the EmonTH.

The first revision of this new design is now available on github here:
https://github.com/openenergymonitor/Hardware/tree/master/emonTxV2.5

and looks like this (im really quite pleased with how it turned out, there's something quite satisfying about designing and routing together a pcb, trying to find neat layouts and so on):

The main features are:

2x CT sensor inputs using higher quality 3.5mm jacks used on the EmonTx v3 and emontx shield
1x ACAC Voltage sensing and power input
Terminal block power, ADC's and Digital IO breakout + full spare IO breakout.
Onboard DS18B20 footprint
Based around ATmega328 + RFM69 core
Fits in emonTH enclosure

The main downside perhaps of this design is that in order to get it into the emonTH case I needed to drop the number of CT inputs down from 3 to 2, the thinking being that most applications are house consumption + solar pv. But Im aware that this does make is unsuitable for 3 phase application, we do want to develop a dedicated 3 phase board design with voltage sensing on each phase so perhaps that's the better option for 3 phase application than using the emontx.

I've sent off for a first prototype PCB from ragworm so will be building and testing this design hopefully next week. Id welcome thoughts on the design and any suggestions and may do another revision before getting these made in quantity.

Common component kit

The other idea we've had is that since the emonglcd and emontx kit share so many of the same resistors and capacitors we could potentially offer a general openenergymonitor throughhole component kit with enough of the common components to build an emonglcd or several emontx kits. Then alongside the common component kit would be the PCB and emontx/emonglcd specific components such as the LCD, connectors and perhaps the atmega. We're' just working out the pricing for this. This could be quite a good option for people who have good home electronics stocks of different resistors/capacitors and could simplify the kitting for us with just one kit with 10x 20x of all the different resistors and capacitors. Interested in hearing people's thoughts on the idea.

This blog post is a repost from the forum thread here: http://openenergymonitor.org/emon/node/10802
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