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Forum Index : Electronics : measuring current computer
| Author | Message | ||||
herbnz Senior Member  Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi I have been trying to convert the output current from turbine to 0-10v suitable to feed a computer type controller with limited success. todate I have set up a shunt in the negative feed indepentantly taken taps of it feed to the opamp. the opamp is connected to the generator side ,the most negative side, and the + input to the battery side. Works but prone to interferance. I can easily program gain and offset in computer. also have requlated the voltage to supply the opamp with zenner. Shunt works OK with 200mv digital meter giving 10mv for 3.5 A. Basicly any better ideas how to achieve this or do I need to just tidy up design here maybe up the shunt output ? Herb |
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| Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221 |
Have you fitted any sort of RF filtering around your opamp? Is it all in one tight area or a big "birds nest"? |
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| herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi Robb Birds nest is dead right yea on to my untidy development al right. Have sorted out a little put cap across feedback seems ok now on test. still would love hear if any other approachs tho it is prone to problems measuring such a small dc voltage right down on the same level as the opamp supply a form of dual supply would be good but kiss principle applies Herb |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5031 |
I had a lot of problems making the PicLog read current accurately and still use common DickSmith components. Spend days on the problem, very frustrating. Ended up using a good old shunt, positive amps only ( it would have been nice to measure drain as well as charging rates, but no joy ).I did find some usefull info in Google. Look for "high side current measurement" and "difference amp". Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Bryan1 Guru  Joined: 22/02/2006 Location: AustraliaPosts: 1211 |
Hiya Herb, Eh mate the ACS754 might be the go here, it outputs about 13mV each amp and the ones I got are rated to 150 amps. Just put the output mv into a AD converter and feed the bits to the computer in binary and let the puter do the decoding. Another way would just use a pic with AD onboard and output the data via rs232. this is one of my many pic projects I want to do but with the farm and work playing with pic's aint got much time these days. Cheers Bryan |
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| Robb Senior Member Joined: 01/08/2007 Location: AustraliaPosts: 221 |
Are you attempting to power the thing of the same circuit you are measuring or has it got its own fully floating power supply? I expect you'd need a totaly isolated supply. What opamp are you useing? |
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| herbnz Senior Member Joined: 18/02/2007 Location: New ZealandPosts: 258 |
Hi Glen yeah we have gone down same track internet interesting all right but as you say making with readly available components frustrating. Byran I looked this unit up Ideal but where did you get one and how much I dont need any AD as the Smart Relay accepts analogue 0-10 or 0 24v also very easy program any gain offsets. I have been really impressed its a developed pic type micro computer screen and all. Robb Yeah using the same supply be lot easier to use isolated supply but not really option unless use batteries or tap off ac side some how maybe with computer controllers etc we may need to go down that track. I am using the cheapest opamp out lm324. I have with peserverance achieved a working circuit that will do a matter tidying up and connecting to shunt so current flow in separate sensing connections. Cheers and many thanks for the input Herb |
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| Bryan1 Guru Joined: 22/02/2006 Location: AustraliaPosts: 1211 |
Hiya Herb, Eh mate those chips come from Allegro, I just registered with them and ordered them as samples  . you'll find alot of electronic companies will send you samples like microchip, dallas, etc.
Cheers Bryan |
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