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4 posts

Wannabe Geek

# 251538 29-Jun-2019 23:33
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Hi, this is a product I've been developing recently. These are actually the first PCBs I've designed as well as the first time I've ever reflowed a board so I'm quite happy how they turned out. I'm keen to get some feedback on whether people would be interested in these and for what price and application. Eventually the goal would be to take the product to Crowd Supply. I've already posted it on an ebike forum I frequent and I've got some positive feedback but I'm unsure if there would be enough interest to actually do a production run at an acceptable price.


The product is an open source bidirectional dc energy monitor. It is designed especially for e-bikes, e-scooters and e-skate as well as rc cars, boats and flying models. It could also be useful for general battery charging and discharging, renewable energy, dc-dc converter testing (including efficiency testing with two units) and some auto/marine applications. It is aimed mainly at the hobbyist market, but I expect some use with more tech savvy general consumers (e.g. on a commuter's ebike) and maybe with some electronics technicians. It has many features such as extremely small size, Bluetooth, data logging and graphing on it's color display, high accuracy and water resistance. The product is basically a big upgrade to the very common watt meters like this one which are sold under many different names:


Not every feature or spec listed below is implemented but my prototypes are mostly working as expected. The display and web interface is mainly for my own use and the end product would have a much better UX. It would be easy to make a derivative design, e.g. a model with a 200A external shunt or a model with different connectors or display. The web app will be mostly hardware agnostic and the firmware is built on Apache MyNewt which makes it easy to run on different hardware platforms with it's Hardware Abstraction Layer and device drivers.


Bidirectional current sensing
Reverse voltage protection
Bluetooth connection
Logging/saving measurements
High voltage support
High accuracy
Open Source
Low power consumption
Extremely low standby power consumption
Web app can be used offline on PC/phone/tablet with Bluetooth LE
Individually calibrated


Amass XT60 connectors
6-120V operation
50-60A continuous, 160A peak
<0.5% (maybe <0.1%) current accuracy
5mA precision
<0.1% voltage accuracy
<0.005V precision
Average current consumption <1mA (could be as low as a few 10s of uA) without display
8-128Mb flash for data logging



Display orientation detection


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5580 posts

Uber Geek

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  # 2267132 30-Jun-2019 09:13
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Looks pretty awesome. Would probably be keen for a play, solar and/or automotive, no idea on price point 😁

'That VDSL Cat'
10649 posts

Uber Geek


  # 2267275 30-Jun-2019 12:06
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Very much as above. I've been messing around with something like this. But esp to WiFi backed.

#include <std_disclaimer>


Any comments made are personal opinion and do not reflect directly on the position my current or past employers may have.


4 posts

Wannabe Geek

  # 2268727 2-Jul-2019 18:56
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If either of you would like to try out one of the prototypes for a while I could potentially drop one off depending on your location or post one.

210 posts

Master Geek


  # 2268734 2-Jul-2019 19:21
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Really nice work! It's definitely a manageable size for a few of the use cases described. 


Production runs could get interesting as you will have seen the prices the simple ones in the RC supply stores sell for. Will be interested to watch the progress.

5580 posts

Uber Geek

Lifetime subscriber

  # 2280208 20-Jul-2019 13:12
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Having a good play, great little gadget.

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