Info request on Doc Wattson / Watts up

[Dave B]

Hello,

 I've been looking at the small common watt meters shown like the Doc Wattson or watts up digital computer type that read out all the goodies. I'd like to purchase something like that but I notice a max. rating of 100 A and wondered if anyone had pushed one to let the smoke out ? If so, is there a bit of over head to that 100 A max. figure ?

 I'll be running a 24 VDC 16' battery charging axial that I've seen  push over 3KW when I was heating direct with it. This at approx. 100 VAC. 300 rpm. about 22 MPH wind. with my other stator. Any comments or suggestions with anyone's experiences with these neat little units would be appreciated. Thank you,  Dave B.

I moved this to Reviews which seems more appropriate. TW

[commanda]

I have a Doc Wattson on my scooter. On their website is instructions on how to crack it open, remove the internal current shunt, and run an external shunt.

Amanda

[zeusmorg]

 Actually, I believe those instructions have been pulled down, when I was looking for info about my watts up, I didn't see them.

[commanda]

Try this:

http://www.rc-electronics-usa.com/special-mods.html

Amanda

[Dave B]

 Thank you Amanda and I checked it out. The only thing I dislike about these is that they are so small. I realize for many applications this is great but I'd like to see one that was more a panel mount size.

 I've been searching and will continue to until I find one similar to what these measure and the way they display and scan. I've seen some that are very expensive and you have to manually select the scale you wish to read too as it only displays one reading at a time.

 Anything out there you know of that basically works the same as the Doc Wattson but is larger I sure would like to know what it is. I'm searching, it's nice to know this will work with an external shunt too. Thank you,  Dave B.

[commanda]

I see 2 options.

Trimetric or DIY.  Don't know much about the Trimetric except that they exist and cost too much.

If you wanna DIY I can help get you started with a Picaxe and a regular 2 line lcd. Write code in Basic and ISP (In-System program) through the PC serial port. Compiler/Programmer even works on Linux :-).

Amanda

[DanB]

Mine gets quite warm when output from the wind turbine is sustained over 80 amps or so - warm enough that the screen 'blacks out' ~ but its always fine when it cools back down.  I've seen mine peak over 140 amps...

I should try to do the external shunt.

[bzrqmy]

Are you letting 140 amps run through those skinny little wires or did you find a way to put larger leads on it?

[RandomJoe]

I have the "Watts Up" version, rarely measure high currents and wanted the better low-end resolution.  Not sure just how many differences there are physically between the two.

The wires on mine are too thin!  The wires will heat up noticeably if I run just 10A for any length of time.  I also (understandably) get a noticeable voltage drop across the meter if I try measuring higher currents.

For 90% of what I use the things for, that's fine - 10A or higher is pretty much limited to when I am checking current draw of a radio transmitter and I don't leave them on my radios full time.  But there have been a few instances where it was a problem.  Never have tried using an external shunt, though.

[Dave B]

Amanda,

  Thank you for the offer to help. I have no experience with the Picaxe and programming. Also, my Vista machine has no serial port, I know there are supposedly USB / serial conversions but I had no luck with a couple to communicate with my Davis Weather Wizard.

  I've got a fair amount of electronics back ground including assembly and have programmed a few AB PLC's with Ladder Logic so I know I could learn. It would be great to maybe save a few bucks over the Trimetric and learn something new besides.

  Any suggestions for me to move forward on this DIY project ? I would welcome your assistance and could certainly pay you for it. Thank you again,  Dave B.

[commanda]

Dave,

This is the starting point I used for my watt Hr meter.

http://thebackshed.com/Windmill/charger1.asp

Have a look, see if it looks like something you'd contemplate.

(I never re-invent the wheel. This had the cpu, lcd, pushbutton switches, and code to tie it all together. Great starting point.)

Also, this is the Picaxe home page.

http://www.rev-ed.co.uk/picaxe/

I see they now have a USB download cable.

Amanda

[scoraigwind]

I am really pleased with my Doc Wattson and looking to buy more but you don't seem to sell them any more at forcefield?

[Dave B]

Must be that those who report well over 100 A output for their machines are either not using these meters, these meters are well under rated or possibly their own way of measuring current may not be accurate. I believe I have measured well over 3KW for my 16' machine and now for 24 VDC if this happens it wil be over 125 A. Thought that would toast the meter's 100 A max. rating unless set up with an external shunt. Might try one, I just wish there was a physically larger version for maybe a panel display.  Dave B.

[Darren73]

Dave,

There are serial expansion cards available that work properly, you just need to get the right one for the expansion slot you have available.

Regards

Darren