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HELP needed with TL783 Regulator Circuit

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by GoGreenElectricsLTD, Mar 17, 2013.

  1. alec_t

    alec_t Well-Known Member Most Helpful Member

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    So the 16mA proposed should switch the SSR fully on.
     
  2. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    Yeah, that should work !.

    I have another question on a seperate issue, nothing to do with this circuit. Using a similar SSR to the one I gave details of previously, what do you think the heat dissipation would be at 90v 6A ?. Im trying to figure out what size of heat sink Im going to need ?.

    Thanks
    Rob
     
  3. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Do you mean dissipation in the SSR itself? I've no knowledge of its efficiency. Obviously the load is dissipating 90*6 = 540W, so if the SSR efficiency were, say, 99% (that's pure supposition) then it would be dissipating 5.4W.
     
  4. dave

    Dave New Member

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  5. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    I thought that you might have more experience with SSR thermal efficiencies and heat outputs. Ive had very little luck getting info out of the supplier. All he suggests is that I purchace one of the purpose designed heat sinks which are designed for the SSR when its working under full load. However the load im putting on it is less than 1/40th of its capacity.
     
  6. Mr RB

    Mr RB Well-Known Member

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    SSR's use a standard TRIAC as the final switching device. It will drop about 1.1v to 1.5v from low current to max current.

    So a 16A rated SSR running at its max will dissipate somewhere near 16A * 1.5v or 24W.
    A 25A SSR running at 16A will be maybe 16A * 1.3v or 20.8W.

    Yes they need a heatsink.

    Also, the SSR is rated for AC mains voltage, and will likely require that amount of voltage to properly operate its internals. You might be able to use a 110v SSR to switch 58v AC but it might not work very well. Really it should be switching 110v AC, and not another AC voltage.
     
  7. alec_t

    alec_t Well-Known Member Most Helpful Member

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    So the FET will dissipate much less power than the SSR, even supposing the SSR is suitable for a 90VDC 11A dump load.
     
  8. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    The SSR is rated at 220v DC 80A. So that means its total power capacity is 17.6Kw
     
  9. alec_t

    alec_t Well-Known Member Most Helpful Member

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    OK. So the dissipation, using Mr RB's figures, could be up to 1.5 x 11 = 16W. That's implies quite a hefty heatsink.
     
  10. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    Well the reason I asked this question is that my existing SSR being used with the Dump Load controls peak currents of 23A at 95vdc but in pulses of twice per seccond with a 0.25 seccond delay between. The longest I have seen it do this before the wind dropped again was for 1 minuet. During that time, the Dump Load got quiet hot, but the SSR fitted to a standard heatsink didnt even break a sweat and I doubt if it got over 30c.

    I have another application where that heatsink would be too large. So I was hoping to get an idea of the smallest heatsink I can get away with.
     
  11. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    Just thought I would post a photo of my new capacitor in use. It seems to be doing a good job, although we have not yet had any stormy weather. So most of the time the voltage is remaining below 80vdc. Today the maximum power its got up to on a gust has been around 250 watts.
     

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  12. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    A question for Alec

    How would I construct a very simple voltage controlled switch. The switch would need to handle 15v at 15mA and to operate at around 43v.

    I was thinking somthing along the line of a small FET with a 43v Zenner, but I dont know how I would connect it up ?. Also if it had some small degree of adjustment between 40 and 45 volts that would be usefull too.

    Rob
     
  13. alec_t

    alec_t Well-Known Member Most Helpful Member

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    If you're not too concerned about trip-point tolerance (say 5%) the circuit could be very simple (not much more than zener and FET). Tighter tolerance would need a more sophisticated circuit.
     
  14. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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  15. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    Yeah I would need to maintain a reasonably accurate trip point, at least to within 0.1v
     
  16. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    Would you be able to chat in the "Chat" room ?
     
  17. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    OK, today has been very windy and whilst the Capacitor has improved things the voltage of the turbine is still knocked back exessivley when the dump load kicks in. So I think the PWM controler is still the best way to go. I will attempt to make the modifications to the SWEA unit that Alec has suggested !.

    Im the mean time if anyone has a solution to my other voltage controlled switch problem, I would be very interested.

    Thanks
    Rob
     
  18. alec_t

    alec_t Well-Known Member Most Helpful Member

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    This should do the trick. If you need a 0.1V tolerance then R1 and R2 should be 1% tolerance. The voltage reference (U1 ), opamp (U2) and transistor (Q1) are examples only, convenient for simulation; other types could be substituted. The trimpot theoretically should give a 40-48V trip-point adjustment. When the trip voltage is exceeded Q1 conducts.
    TripSwitch.gif
     

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  19. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    OK, thanks for that !.... I will have to order some vero board and get the components off Ebay then :eek:)

    I have a system set up which puts all the exess renewable power I generate into batteries. As frequently I am generating far more than I am using. So rather than power my neighbours house, I put the power into batteries and then use it myself later on.

    My charger has a high and low power state, which can be switched remotley by a sensor. This has nothing to do with the 4 stages of charging and is simply a current limiting option. I have two sensors on the renewable feed line, which sense how much power is being generated from both Solar and Wind. When the power exeeds 600w the charger switches ON in low power mode, this ensures there is always enough power to run both my home and the charger without drawing anything from the grid. When the power exeeds 900w it then switches over to high power mode, usualy between 11AM and 3PM when the sun is high in the sky.

    The problem I have been experiencing is this. Late in the afternoon when the batteries are in the final stage of charging the power drawn by them is low. So the last thing I need is for the charger to suddenly switch itself down to low power state and drop the charge current even more. By having a voltage controled switch it will enable me to force the charger to remain in high power mode even when the sun is going down. But ONLY when the battery voltage exeeds 43v....... with 44v being at float level.

    I hope this clarifies my need for the voltage controlled switch.
     
  20. GoGreenElectricsLTD

    GoGreenElectricsLTD Member

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    Ive been looking at the cost of components on Ebay and I dont think im going to be able to build this for much less than £20.00. Which is a bummer, because there are products already available which will do the same job for around £27.00

    http://www.ebay.co.uk/itm/390562695171?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1438.l2649
     
  21. alec_t

    alec_t Well-Known Member Most Helpful Member

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    Now that you've explained what the switch will be used for it's apparent the circuit I proposed would probably need some modification. For example, the supply to the voltage reference may need a decoupling cap, some hysteresis may need to be added, and if the switched load has any significant inductance there should be a freewheel diode from Q1 collector to the +15V line.
     

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