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Forum Index : Electronics : Inverters
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catchnthe-)))) Newbie  Joined: 03/01/2009 Location: United StatesPosts: 24 |
Hello,Just getting a bit closer to running wind turbine. At a point for a Dump load purchase. I built a 12 volt air exchanger from A old dryer element. But want to heat water also. I will purchase a 12 to 120 volt inverter for A back up for 120 hot water circulator pump. Can a turbine be hooked directly to a inverter then to a 120 volt immersion water heater. Or must battery always be in this circuit. Thanks Chuck Freedom allows us a lot "Please don't abuse." |
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Bernie the Bolt Regular Member  Joined: 26/10/2006 Location: United KingdomPosts: 45 |
A charge controller would switch from the batteries to the inverter when the batteries are fully charged. My undertanding is that the batteries must always be in the circuit to hold down (stabilise) the voltage wich would other wise rise to perhaps 48volt. Bernie the Bolt I'd rather be sailing! |
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| Janne Senior Member  Joined: 20/06/2008 Location: FinlandPosts: 121 |
Hello, The easiest way would be use a battery to clamp down the voltage. You might get away without using one, but then you would need to design the controller very carefully so ot will not let the voltage raise too much to damage the inverter / cut it out. On the picaxeforum was just recently a discussion about a similar system, you might want to look at it if you want to build the controller yourself.. there the configuration includes batteries. The discussion can be found at: discussion If at first you don't succeed, try again. My projects |
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GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Janne, the problem that was raised in the discussion link. without jumping onto this other forum This can be done with a picaxe08M, using a single analogue input, say ADC10 1, and outputs 0,2,4. The pin3 input would not necessarily be needed. A 1 second or so timing loop, a few counters some decision testing and a few loops would do the trick. The use of a picaxe 28X is probably overkill. I would use a 10bit input resolution. I have just configured a cct that controls a diversion loading on a 2.5kW windmill, that uses a picaxe 08M, and 2x240VAC SSrelays. The windmills see a varying range of winds, and sometimes storm events, but are never in sustained maximum output winds for any periods more than hours. One relay controls the diversion load, 1kW, and the other disconnects the windmill, which actually enables an electrical brake within the windmill. One switched output from the battery controller, indicating that the battery is above or below the variable set point [depending on battery state of charge] is used. The windmill output varies considerably and the picaxe monitors the need for diversion activity at 50mS intervals. If the diversion is on for 30 consecutive seconds, the windmill is shut down [for 5mins] as it is probably too windy and the battery is quite charged. As long as the diversion turns OFF within the 30 second timing, the windmill stays ON, and continues to try and fully charge the battery through all stages of the charging cycle, using the diversion load to bleed OFF power. A second output that is a battery overvoltage sense is used to override and shut the windmill down. WRT the discussion above, I would not be too concerned at say even a 2 second minimum ON period for the elements. The use of relays is likely to be problamatic in the long term, so if a micro is used, just use mosfets, and if necessary additional rectifiers. The use of fixed voltage settings and not variable settings that change depending on battery state of charge, will probably lead to diminished battery capacity over time. When voltage is at 25.5V turn on heating element 1 When voltage is at 26.3V turn on heating element 2 When voltage is at 27V turn on heating element 3 When voltage is at 28V turn on heating element 1 and 3 When voltage is at 28.7V turn on heating element 1, 2 and 3 In periods of low winds, the battery will be held at below 25.5V. This will reduce battery life. This reigime will make it difficult to maintain an absorbtion phase in the battery and the cells will likely sulphate. I will have a look at some picaxe08M code and if it is promising, I will post it. Gordon. become more energy aware |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Hi Gordon, This job should be easy picking to do with an axe.. It might be even nicer, if the control of the disconnect(=electical shut down) was controlled with an anemometer. Though if it was mine, I'd just add a reset button to be used after a storm instead of the automatic restart. If at first you don't succeed, try again. My projects |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Janne, here is the code. This is for a picaxe 08M and this would make a simple dedicated component. The program has instant ON of relays, with the delay OFF. the watchdog timer is 500mS and the outputs are held on for 20 timing intervals after being triggered. The choice of elements can give a doubling of the loading per stage. The requested delay in turning OFF the outputs will give some increased loadings at certain stages until the individual timers lapse. There are some anotations describing scaling etc. ' output 0,1,2 used to activate heaters ' heater 1 has 1 unit of loading ' heater 2 has 2 unit of loading ' heater 3 has 4 units of loading ' stage 1 turns loadings OFF ' stage 2 gives nom 1 unit of loading ' stage 3 gives nom 2 units of loading ' stage 4 gives nom 4 units of loading ' stage 5 gives max 7 units of loading ' the loading at each stage may be higher due to ' the required turn OFF delays ' the stages give an approx doubling of ' the load for each stage change ' use input 4 to read battery ' change the lines of code * to suite the ' voltage scaling and stage settings symbol volts=W0 symbol counter0=b4 symbol counter1=b5 symbol counter2=b6 counter0=1 counter1=1 counter2=1 main: pause 500 readadc10 4,volts volts=volts*50 ' * if volts < 25000 then stage0 ' * if volts < 27500 then stage1 ' * if volts < 30000 then stage2 ' * if volts < 32500 then stage3 ' * if volts > 32499 then stage4 ' * stage0: gosub lower0 gosub lower1 gosub lower2 goto main stage1: high 0 counter0=20 gosub lower1 gosub lower2 goto main stage2: high 1 counter1=20 gosub lower0 gosub lower2 goto main stage3: high 2 counter2=20 gosub lower0 gosub lower1 goto main stage4: high 0 counter0=20 high 1 counter1=20 high 2 counter2=20 goto main lower0: counter0=counter0-1 if counter0<1 then low 0 counter0=1 endif return lower1: counter1=counter1-1 if counter1<1 then low 1 counter1=1 endif return lower2: counter2=counter2-1 if counter2<1 then low 2 counter2=1 endif return goto main end become more energy aware |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Hi Gordon, The code looks good to me, should work great. Mayby you want to share this at the picaxeforum too.. If at first you don't succeed, try again. My projects |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Janne, already there. Gordon. BTW the few examples of code given seem far too complicated for the task. The simplest chip will do the job. Chances are that using the 28x1 that most of the chip will not be used. The original poster used double opto coupling as well. I would have just used a small direct coupled small logic mosfet to interface the SSRelays. A lot less current and probably no need for the 2 regulators, if just a resistor and 4V7 zener supply was used. The SSRelays have 3-32V inputs as well, so no need to power from the regs. probably about 14 components needed, instead of the number used. The board could end up about 25mm x 25mm only. The SSRelays could be used to mount the pcb as well, but this would make the board bigger, but assembly simpler. I hope the person uses the 28X1 for a better purpose. become more energy aware |
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| Janne Senior Member Joined: 20/06/2008 Location: FinlandPosts: 121 |
Yes, 28x1 is overkill for the appliance.. though it might prove useful later if he wants to add something else on it later. You get the 08M for 1.5£, and the 28x1 for 3.99£, so for one time use it's not too much of a difference. For bigger production 08M would be the choise. I disagree with the use of a zener regulated supply, as the supply voltage is used as the reference in ADC measuring. It needs to be as accurate as possible, so regulator is the best choise. If the zener is to be used, then the only option would be to use 20M or 20x2, which can use the calibADC command to compensate for the varying supply voltage. The optos are a nice insurance about any nasty voltage spikes, but are propably unnecessary. Though they leave one less thing to doubt if problems are encountered. The pic / picaxe seems prone to suffering from transients.. at least many posts about interference on the picaxeforum. If at first you don't succeed, try again. My projects |
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| GWatPE Senior Member Joined: 01/09/2006 Location: AustraliaPosts: 2127 |
Hi Janne, This cct does not require absolute accuracy. The exact values for the comparison values would be read from the picaxe at the desired setting point and set in the picaxe program code. The slight changing of the 5V rail with changing input voltage or pin loading will cause slight positive or negative feedback WRT ADC conversions. increased pin loading causes positive feedback and increased battery voltage causes negative feedback. If you use an LP2951 type regulator then the power consumption would be OK, but a std reg consumes too much power in my applications. Transients are usually caused by insufficient input pin bypassing. Gordon. become more energy aware |
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