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Forum Index : Electronics : Questions on a charge controller project
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| Pukwudji Newbie  Joined: 10/07/2009 Location: United StatesPosts: 20 |
I'm building a charge controller based on the one found on this site: http://www.mdpub.com/Wind_Turbine/. I've made a few minor changes and am considering another but I'm not sure how to accomplish it. This is a shunt controller so if the batteries get full it redirects the incoming current to a dummy load. What I'm considering doing is seeing if I can add to the circuit so the circuit can tell if there is nothing connected on the dummy load output and if so have it instead short the inputs (I'd probably include a button to purposefully short the input as well for braking). My thinking is that while shorting the input is not the preferred method it is better than having the circuit try to dump to the dummy load and have nothing there, allowing the turbine to freewheel. This would allow for hooking the controller up without a dummy load in the right circumstances or just be a protection in case the dummy load was either not hooked up properly or experienced some type of failure. My first question is, are there any arguments about this being a bad idea? Next, I'm just learning electronics so don't really have the expertise to design this new portion of the circuit myself. Anyone have any ideas or reference links they can provide for something that could do this (if resistance equals zero then trip this relay)? My last question is how can I determine what the capacity rating for this controller would run? Is that solely based on the Diodes, Fuses, and circuit (trace or wire) capacity? The circuit for the charge controlling itself has only a low amount of power going through it so I'm just guessing it is the rest of the components that would dictate the current capacity of the entire product. Direct information or links to pertinent online materials welcome. Thanks all, Brian in Oregon -Brian V Hillsboro, OR (USA) KF7DUZ |
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Hi Brian Have a look at Gizmo's Charge controller here... http://www.thebackshed.com/windmill/articles/TL084-Controlle r.asp As it will do the monitoring you wish for the dump load. What you would do is set it to cut in a little bit higher than the existing controller. So if there is no dump connected or you have a faliure the voltage will rise above where the normal dump would cut in, and be sensed by the 2nd controller and switched to what ever you choose to connect to the relay..Short or 2nd dump, etc. Pete. Sometimes it just works |
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| Pukwudji Newbie Joined: 10/07/2009 Location: United StatesPosts: 20 |
That seems awfully complicated. Can I not simply use some type of gate to detect when there is no resistance on a circuit and use that gate to trip a relay? I was thinking I could feed low voltage to the dump circuit and compare the voltage coming out the other side to an extremely low voltage (<1v) from my main circuit (through diode to prevent power going back down this part of the circuit if the dummy is actually present and power is dumped to it). If the dump circuit voltage is lower than this feed (like 0) I could then trip a dpdt relay which would short my + and - source leads together. I still have two gates on a quad OpAmp and two gates on a quad NOR gate in my main circuit that aren't doing anything right now. I could very likely be wrong and oversimplifying this as I'm still pretty new, but I'd hope to add this function without doubling the size of my current circuit. Thanks, Brian -Brian V Hillsboro, OR (USA) KF7DUZ |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Ok i didnt look at the circuit before and just had a quick look now. The circuit shows a dual opamp not a quad so i guess you have changed this. Yes you could fudge something like you surgest and even get away with only the 2 remaining NOR gates but i see it a problematic method that might not be reliable. As the controller is the last line of defence between overcharging and or destruction i would want more reliable proven method. SO if you do have 1/2 the opamp spare and 1/2 the NOR gate spare than why not just double the present circuit as its only a few resistors and a pair of trimpots, then set one circuit slightly higher than the other, that way the higher one should never activate unless you have a problem with the main circuit. ( being the lower set one) The same Vreg will do both circuits. It is the battery voltage you really need to monitor and dont give a dam about the dump load. You could even set it up so the mill shorting relay was held closed for normal operation and was unlatched by the 2nd circuit, this way if power was lost to the system at any stage the relay would dropout and inturn short the mill. A fail safe method. This is used by some other members here on larger AXFX mills, but it do mean the relay is always drawing power. Pete. Sometimes it just works |
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