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40V/5A Watt Meter Kit

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iloveelectronics:
A while ago Martin reviewed an uncased watt meter I sent him:

http://www.youtube.com/watch?v=cCd2DDoz38g at 25:35
http://www.youtube.com/watch?v=VBxwdkOyf2I at 26:06

I had a number of those but they sold out very quickly and unfortunately the manufacturer decided to discontinue to product so I couldn't get more of those anymore. I have since tried to look for an alternative and tested a few until I found this kit which is based on essentially the same circuit using the same ATTiny26L microcontroller, running the same firmware from the original designer. The main difference is that this kit is smaller in size, and that it comes with an older version of the firmware. I have finally learned how to flash new firmware on to the chip so I am now ready to start selling these, with the latest firmware (same one Martin reviewed).

The following are a few pictures of the kit, before and after assembling. The LCD panel that comes with the kit has no backlight. I'm pricing the kit at $14, worldwide air mail shipping included (no tracking). If you want tracking I can send it using registered air mail for an additional $2.4. I can also offer a backlit LCD for an additional $2.5 (you will get 2 LCD's in that case, one with the backlight and one without).

Either leave a message here or contact me via PM if you're interested. Thanks for looking!

Cheers,
Franky

SeanB:
Nice, Can I get a copy of the firmware?

iloveelectronics:
You can download it from the original designer's website: http://blog.21ic.com/user1/4577/archives/2007/43308.html

You will see a link that says "UploadFiles/2008-3/12052445228.rar" about 1/3 down that page and that's the last version of the firmware he released. It's only a HEX file though and no source code. I think I did contact him once about the source code but didn't get any response. Perhaps I'll try again some time.

The files have Chinese file names though so you might want to rename them after downloading.


--- Quote from: SeanB on April 29, 2013, 12:21:48 PM ---Nice, Can I get a copy of the firmware?

--- End quote ---

birrbert:
HI Franky!

Could you please post the size of the assembled meter? I'd like to know roughly how much space (length, height, depth) it needs.

Also, do you have any info about the resolution and the accuracy? Maybe a photo while the meter is turned on and taking a measurement?

iloveelectronics:
The assembled meter measures (roughly) 84mm (L) x 38mm (W) x 28mm (H). There is, however, a metal tab that holds the LCD to the PCB that doesn't sit too well with the connection terminals, which actually didn't come with the original kit but I thought they would make connections easier. See the attached picture. That makes the meter a bit thicker on one side than the other. That should be fixable by either removing the tab or not using the connection terminals.

I have also included a few pictures of the meter taking some measurements. I powered the meter with 3 AA size batteries (so not exactly 5V). The input is connected to a power supply. Output is connected to an electronic DC load (the Maynuo M9712 Martin reviewed). Multimeter (Brymen BM-521) is connected to the output (load) end.

I tested the meter at about 2V/100mA, 5V/500mA and 20V/3A (my power supply can only do up to 20V). There is some voltage drop in the leads between the power supply and the meter, as well as between the meter and the DC load. But as you can see in the pictures, the voltage readings of the meter and the Brymen are pretty close. The current readings on the meter and the DC load aren't very far off either across the range.

Hope this helps.



--- Quote from: birrbert on April 30, 2013, 07:17:48 AM ---HI Franky!

Could you please post the size of the assembled meter? I'd like to know roughly how much space (length, height, depth) it needs.

Also, do you have any info about the resolution and the accuracy? Maybe a photo while the meter is turned on and taking a measurement?

--- End quote ---

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