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Forum Index : Electronics : A new controller circuit
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sparkey Senior Member  Joined: 15/06/2011 Location: AustraliaPosts: 819 |
ok thanks glenn my generator has a built in clamping cctry so you never see a full sinewave at the outputs... technicians do it with least resistance |
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| larny Guru  Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Thanks for explaining that Glenn, I had a feeling that Sparkey was asking for a different circuit to my version of your circuit. So my understanding (& please correct me if I'm wrong) of a Dump Controller is this:- Using your figures, the relay operates when the generator voltage reaches 14.5 Volt & releases when it falls to 13.0 Volt. This is what my version does. When the relay is operated, the make side of the change over contact connects a dummy load across the generator output. So, I assume that there is a diode in series between the Generator & the Battery so the Dummy Load does not drain the battery also. So, if that is the case, I don't see any difference between a Dump Controller with a diode & a Diversion Controller with a change over contact to divert the Generator output to the Dummy Load. However, there is a difference; since the C/O contact disconnects the battery, then the voltage spikes will be an issue since the battery is not there to attanuate them. Sparkey, I'll await Glenn's response before proceeding further. Len |
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| Don B Senior Member Joined: 27/09/2008 Location: AustraliaPosts: 190 |
Hi Glenn, I am coming way to late into this thread, but I would like to make a couple of comments on comparator based circuits. The first is that if your circuit needs a comparator function with a sharp switching point, then a comparator is probably a better choice than an op amp. Generally, you need to add some external hysteresis to get sharp switching from an op amp, and this leaves an appreciable dead band. Sometimes though, this is appropriate in a dump circuit, etc. The TL084 FET op amp has a very high input impedance, but you need to be careful not to set it up to compare input voltages that are too close to its supply voltages, as, particularly close to 0 V, it will do peculiar things. When you have to divide the sense and references voltages down to compare them, you need to keep these voltages as high as possible (ie use as little division as possible). This is because the least hysteresis voltage that you can get tends to be a fixed value, and the more that you divide down the sense and reference voltages, the bigger the percentage change in switching points your hysteresis will make. While your sense voltage ordinarily needs to be at least a couple of volts below the comparator supply voltage, less maybe a further margin, if you divide your sense voltage down to, say, a quarter of the supply voltage, then you have degraded the accuracy that is possible with your comparator circuit. Sorry for the lateness of the comments in this thread. Regards Don B |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Don B, Did you see the circuit that I posted? What you're saying above is essentially what I did in my version. Thanks for the input, please offer more as appropiate. Len |
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Almost, but omit the diode. The wind turbine alternator is connected directly to the battery, minimising losses. The dump load is placed across the battery, effectively draining it, bringing its state of charge, and therefore voltage, down. If the windmill is capable of making 300 watts, then the dump load would need to drain off more than that, say 400 watts. So in strong winds, when the battery becomes fully charged, the dump load is switched across the battery and drains off 400 watts ( 300w from the windmill and 100w from the battery. ). This keeps the windmill loaded, and discharges some of the battery charge. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Glenn, may I suggest not to try this arrangement if there is also a solar panel charging the battery bank. In that case you could have a fully charged battery bank (from solar) and no wind, with the dummy load getting switched in and wasting power. I use a relay with a changeover contact to prohibit the dumpload ever being connected to the battery. Klaus |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
It would still work as a charge controller for solar. Remember the charge controllers job is to protect the battery from overcharging, and that can happen with solar as well as wind. If it was a solar only system, you could do away with the dump load all together and use the relay to open circuit the panel, use break contacts instead of make contacts. But if there is a windmill in parallel with the solar ( not recommended, could damage the panels in certain fault conditions ), then a dump controller or divert to dump controller is needed. Diverting the windmill to a dump load, instead of just connecting the dump load to the battery, works OK too, but there are issues. The dump load needs to be able to operate at a wider range of voltages, meaning you cant use light bulbs. With a dump controller, you can use cheap 50 watt bulbs as the load, as they will only ever be operated at their design voltage. But with a diversion controller, the voltage can swing around, so you need a purely resistive dump load ( light bulbs are sort of active, their resistance changes with voltage ), like heater elements. Also when the dump load cuts in, it will slow down ( hopefully ) the windmill or bring it to a near stop, saving wear and tear, but meaning it needs to get back up to speed when needed. Also, there are some nasty electrical spikes and growls when you divert to a dump load and back. It's a personal preference I think. I've run both, both have good and pad points. But the dump controller is the simplest and less likely to cause problems. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Glenn, It seems a pity to load both the battery & the generator. This is a waste of energy. You said above, that my suggestion re inserting a diode is undesirable as it would drop the voltage. Here are 2 suggestions:- 2. Have you considered using a Schottky diode? As you know, they have a lower voltage drop than silicon ones. If necessary, you could connect several (Schottky's) in parallel to reduce the voltage drop. 2. The alternator has a 3 phase rectifier. So if the anodes of these diode are accessable, then you could connect the load resistors as shown in the drawing & thus a diode would not be necessary & thus there would be no additional voltage drop & the battery would not be discharging into the dummy load. Moreover, the resistors will dissipate less power & thus can be of a lower power rating than otherwise. Len 
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
you dont appear to have one of the phases loaded is it that the other phase is not nesscary... technicians do it with least resistance |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Yes, sorry, you're right. Drawing error. I'll fix it & replace. Edit. I could not edit my previous post, so here is the modified drawing. Len 
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
dont missunderstand me here but has glenn stated which type of generator he is using ...star/delta... i guess a star always has a neuteral well then mine must be a delta because it only has three wires comming from it i did not make it myself it is a bought unit ....500 watts technicians do it with least resistance |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Sparkey, No Glenn did not tell me whether he has a star or mesh alternator. I drew a star configuration as a guess. However, it makes no difference to my circuit. The resistors are connected between the alternator & the diodes. Len |
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
also a delta has a different wireing configureation and would require a different diode bridge...but the relay load should be the same.... technicians do it with least resistance |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Yes, it has 6 diodes rather than 3, but there is no difference as far as we are concerned. The main question is whether you can access the coil terminals. The secondary question is whether making this mod will affect your warranty. I can't answer these questions, so I'll leave it to you & Glenn. Len |
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
my apologies i was not out to upset you technicians do it with least resistance |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Sparkey. I'm not upset about anwthing. I was simply saying that I can't answer the questions that I raised since I don't have a windmill or know much about them. So I need you and/or Glenn to answer the questions. Len |
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
my generator has an output lead so there is no problem with getting access to my conneting ...i have had it set up for approx five years so the is no warrenty on it as far as i know i was really interested in the controller cct for my panels but thought that i could help in some way...also i cannot speak for glenn as he is prolly 1000 miles away from me if he has any assembly experence it should not be diffucilt to hack one of these ccts out on vero board as it is not complex the only terminals need be the the power to the board and the terminals for connecting the relay coil as far as i can see i would at a guess be able to knock it out in an afternoon as long as i have all the parts....depending on the cct and its structure i can add jumper pins for different voltage ranges and add in the extra diodes... also have a term block for the "Rx resistor " to match up with the coil resistance....and probbly have the calibration resistors on board with the jumper pin conneting them in and out when needed... technicians do it with least resistance |
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| larny Guru Joined: 31/10/2011 Location: AustraliaPosts: 346 |
Sparkey, The prototyping PCB I often use is the JayCar HP-9558. See:- http://www.jaycar.com.au/productResults.asp?keywords=hp-9558 &keyform=KEYWORD&SUBMIT.x=22&SUBMIT.y=14 Altronics also have one, but it appears to be different. I can't see the detail of the tracks on their web site. See:- http://www.altronics.com.au/index.asp?area=item&id=H0717# I'm not sure what you mean by "my generator has an output lead so there is no problem with getting access to my conneting" Does this mean that you can connect wires to the alternator windings BEFORE the diodes? I'm waiting for Glen to respond to my post to hear his opinion on my proposal. My understanding of what you want is as follows:- Operate the relay if the voltage is > 40 Volt. Release the relay when the voltages is < 28 Volt. When the relay is operated, it will connect the dummy load to the alternator as in my previously posted, hand drawn drawing. Is this what you want? I have a design almost ready to post, but I want to be sure that I have done what you want. Len |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
To answer some of the questions raised. For the sake of simplicity, we'll stick with 12 volts. Yes, draining power from the windmill and battery is a waste of power, but thats the idea. We have an excess of power, the battery is starting to overcharge and the windmill is still producing power, so we need to waste the excess. It need not be wasted though, some installations have a 12volt heater element plumbed into the hot water service, so the excess is used to help heat water, or you could use the excess power in other ways. One advantage of a purely dump load controller, is the dump load will only be operating at 12v, so like I've said, you can use 12v 50watt downlights, very cheap. If you use a diversion system, the dump load needs to be able to work with a wide range of voltages, and this is more expensive than 12v bulbs. A diversion controller, like Len is describing, and which can also be done with a changeover contact as Tinker has done, works fine, but it depends on how you want to run your windmill. If you use a dump controller, as the load is switched in and out, the windmill continues to supply 12v and the same watts, give or take a small %, so its mechanical characteristics wont be affected, like RPM, furling, etc. There are no sudden changes, no spikes in power. For a diversion controller to work correctly, as the dump load is a resistive device, and the alternator is a very active device, the dump load needs to pull the windmill rpm down to near 0 rpm as quickly as possible. This is due to the power cubed nature of wind power, ie, if a windmill is making 200 watts in 20kmh wind, then its going to make 800 watts in a 40kmh wind. A diversion dump loads needs to handle the worse case. A regular dump controller has the battery to absorb surges in power, it clamps the voltage. A diversion controller also has to deal with the inductive spike from switching the dump load in and out, again, absorbed by the battery in a dump controller. Plus the windmill needs to speed up to operating speed when the load is removed. There is a whole bunch of other stuff that I dont want to go into here, windmill alternators are interesting beasts, and there is a reason they call the output "wild AC". With a batter permanetly connected, its kept under control. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| sparkey Senior Member Joined: 15/06/2011 Location: AustraliaPosts: 819 |
ok since glenn was the first to ask about this controller publish his cct i will build it to your specks and if glenn wants i will ship it to him ..post and deatails lator .... secondly yes could you please publish my ask of the 40 volt version...thanks sparkey... and i will check out the other prototyping boards you mentioned ...before i decide what board i will use.... technicians do it with least resistance |
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