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Forum Index : Electronics : new member that needs help
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| kale franklin Newbie  Joined: 24/01/2014 Location: United StatesPosts: 3 |
my name is kale. i have an associates in industrial electricity and i have been a maintenance man for the last 10 years. i work on everything from 12 vdc systems to 480vac systems. part of my job is to build and program "smart fixtures" that are controlled with a PLC and touch screen HMI's. one of my hobbies is building my own solar power system as a back up for when the power go's out, and i also use my batteries for when i am working in my garage. i can run my radio, charge my phone, and operate small power tools. my panels put out a peak of 45 watts to charge my 2 battery bank with a PWM charge controller. you can see my projects on http://www.instructables.com/tag/type-id/?sort=none&q=kalefr anklin now all that introduction being said..... to improve on my system i am looking for 2 items. i am cheap so i dont want to pay what i think are high prices for something i can build. 1. dump load control. i have seen some on this site and i am wanting to know more. in my job i just connect electronic parts and follow the instructions. when it comes to understanding more about the exact operation of each electronic component on a board i am not the best. i want a very simple control that at 100% battery charge it turns on the relay and a 90% it turns off. what i want to know is how using a PWM charge control, and latter a MPPT controller, going to affect the dump load circuit? currently i am using this kind of controller, this . i have seen others that connect there relay into this some how. it is an option, but i would prefer a separate dump load control. right now when the batteries are full the charge controller just disconnects the batteries from the charge. with a dump load controller i want to add a grid tied inverter to make use of that extra power. 2. sun tracker. i have some old 12vdc motors that i am going to use. the circuit board only needs to be powerful enough to power the forward and reverse relays, the relay will take the motor load. a night time reset would be nice, but not necessary. if there is a reasonably priced units out there that i have not found online please let me know. otherwise i am all ears for what i need to build these 2 projects. |
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powerednut Senior Member  Joined: 09/12/2009 Location: AustraliaPosts: 221 |
Hi Kale, and welcome. A dump load controller can be as simple or as complicated as you want really. Most of the time on here we are talking about using them for wind turbine control as wind turbines shouldn't just be disconnected from the batteries. There isn't any reason why you can't do that for solar though. If you want to design and build it yourself it is probably easiest to treat it as a almost completely seperate circuit to your PWM or MPPT charge controller. That way the PWM or MPPT charge controller will just go ahead and merrily push all the power they can into your batteries, and your dump load just monitors the battery voltage. When its full, switch on a relay to connect your grid feed inverter. When its at 90% or below, switch off the relay. If you want to complicate it, you can add another input to check if the solar panels are outputting power, and only operate the relay when they are. Electronically there are a number of ways of implementing this. The dead simple "overkill" way is to use a cheap microcontroller. just use a voltage divider to sense your battery voltage, and output to a relay. a simple power supply circuit and your done. For other dead simple ways to do this do some research on op-amp based comparator circuits. There are a number of circuits on the back shed site that use these. Check out the simple charge controller for an example: here You could probably use that circuit as is. just remove the wind turbine and rectifier (3 coils and six diodes on the far right), connect your grid feed inverter instead of the 0.1 ohm load resistor and connect the battery to the middle pole of the relay, rather than the top. and finally, check out the ghurd controller (ghurd controller here ), which again does pretty much exactly what you want. use the output nfet to trigger the relay, rather than a dump load and job done. Have fun with it... |
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Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
just posted one http://percul8or.blog.com/2013/12/29/wind-turbine-charge-con troller/ |
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Downwind Guru  Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Its Best to use the link button to insert a link in your posts, as the link above is broken, this is often caused by the forum software preventing Spamming. http://percul8or.blog.com/2013/12/29/wind-turbine-charge-con troller/ Sometimes it just works |
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| powerednut Senior Member Joined: 09/12/2009 Location: AustraliaPosts: 221 |
and yep, percul8or's uses the op-amp comparator method as well. |
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| Downwind Guru Joined: 09/09/2009 Location: AustraliaPosts: 2333 |
Well it is the most basic type of chip to suit the application, no rocket science there. The varisitors are a interesting idea, yet to get my head around the logic behind the idea, to me it appears as .............magic smoke out = runaway mill, ...where as a fencing wire dumpload resistor means bullet proof. Some component values to the schematics would be a handy thing. Well done for your effort, but im still reserved to the control method. As you quoted its a hybrid of several other designs, good on you for doing it. Putting boards up for sale without beta testers can be dangerous. Good luck. Pete. Sometimes it just works |
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| Percul8or Newbie Joined: 09/08/2010 Location: AustraliaPosts: 13 |
Hi Pete and others, Thanks for the feedback guys. Yes I just noticed the extra space in my link causing a problem. I'll fix that Also FYI I have had 3 prototype units (vero board) out on test for over a year. One on a 600 watt turbine and the other 2 on 300 watt units. All have survived in winds over 120km/h. Prior to that I have had 2 x 300 watt 48V units using only 3 thermistors in total of lesser capacity running for over 5 years. The turbines can get to 500 watts but as I run them in MPPT mode the volts also get to 150 volts (cut off) 500w/150v=3.33 amps ie not a lot of current The thermistors I use here are rated @ 7.5 amps each. So 7.5 x 6 = 45 amps of capacity So 600 watts @ 26.5 v = 22.64 amps and to be safe 800 watts @ 26.5v = 30.18 amps So plenty of safety margin here. Funny I look at fencing wire as more dangerous as it can simply melt the turbine coils due to harsh stopping. Something I have seen first hand and the reason I designed this. In fact melting the coils is a great way to brake the turbine. It just never starts again 
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