Automating a Briggs an Strat battery charger

[Old F]

Automating a Briggs an Strat battery charger

Things are starting to fall together  on a project I have been wanting to try for a long time.

And that's to have a  home brewed engine gen set  start and stop its self depending on

battery state of charge.

The stopping part is easy  you use a dump load circuit like Hugh has in his plans and on his web site.

In stead of turning on a load you use the relay as an engine kill switch.

The starting part is a bit harder I will be using  a SL99 PLC from  http://www.splatco.com

After looking at different programming soft ware there's was the easiest  for me to get my head rapped around. No doubt  some ware there is something easier and cheaper but I haven't found it yet

But now that I have bought one I will probable find two or three the way my luck runs :  )

I will be using a ½ HP PM motor as the starter and generator a quick and dirty  test showed it would start

the Briggs easily .

Here is my program for the PLC    For the folks who this type of programming is old hat please don't laugh. :  )     I am use to programming in ladder and am still learning the ropes .

Every thing works ok in the simulator all I need to do is work on how to confirm that the engine is running for input two.   The program allows for three start attempts then sounds an alarm an waits for a reset.    

Here is were I am at for now  so many projects so much fun so little time :  )

Old F

        * GEN START 04  

a1    waiton    0    *  low battery voltage start gen

    on    8    start relay closes      

    pause    4    * for 4 s

    off    8

    goifinon     2,a4    * engine running

    goifinoff    2,a2

a2        on    8    *start relay closes      

    pause    4    * for 4 s

    off    8

    goifinon  2,a4    * engine running

    goifinoff    2,a3

a3    on    8    *start relay closes      

    pause    4    * for 4 s

    off    8

    goifinon     2,a4    * engine running

    goifinoff    2,a5

a4    waiton    3    * battery  full charge stop engine   

    on    9

    pause    15

    off    9

    goto    A1

a5    on    7    engine fail alarm

    waiton    10    * fail alarm reset *

    off    7

    goto    a1       

[Norm]

  Have you ever thought of a windpowered battery

charger with Briggs & Stratton engine as backup

....The windjenny would charge the battery with a

small pm motor in series with the battery....motor shaft has a flywheel on it...if the wind dies down the flywheel slows a belt drive engages the engine to the flywheel to maintain the flywheels constant speed.

 



            Well maybe clear as mud?

             ( :>) Norm

[sh123469]

I was going to ask how you were sensing engine in operation.

How about a small coil pickup using the flywheel magnet?  You could setup a relay to close when the engine gets to running speed.  Close the relay with power from the coil.  Sense the relay closure with the PLC.  A resistor should be enough to control relay engagement so it doesn't happen below a certain RPM.  Another thing, once the engine starts, it might take a few seconds to get up to speed, especially with a load.  You might want to pause for a couple seconds before checking if engine is on after starting relay is disengaged.

I also didn't see how you are measuring the battery voltage.  I assume there must be some analog to digital setpoint that has been programmed.

Hope I made a suggestion that will be of use to you.  It has been a long time since I programmed PLC's.  I did mostly ladder logic programming too but did a couple of projects with small text based programmers.

This could be easily done with a picaxe controller or pic for less money but would require you to build the interface circuitry to connect everything.  The programming language is very similar for the picaxe.

I have been thinking about using a picaxe for the blower controller in a solar hot air heating collector.  $3 chip, $2 temp sensor, few resistors & caps, small relay.  $10 or so for on off, progammable blower control.  Either small wall wart or solar & batteries for power.  Will run from 3 to 5.5v.

I will be interested to hear how your project turns out.  If you energize relays with your PLC, don't forget the back-emf clamping diodes.  I know it's basic, but easy to forget.

Steve

[Old F]

Norm

This will be the back up for a wind generator. Its like the old 32 volt Delco light plant but 12 volt.

If there is enough  wind to keep the batteries charged it will just sit there and come on only when needed.

Steve

I am planning to use something like Hughes dump load circuit for voltage sensing and use the relay contacts for the inputs. I will be putting a pause  before   goifon  2,a3 to give it time to check for voltage at the generator as there will be a blocking diode between it and the batteries .

The nice thing about the  splat PLC it has the clamping diodes are right on the board.

I use to do a lot of board building but the old eyes are not what they use to be  so I like to keep the parts count  small and the parts big : )   After I get this part running  I plan on trying to use a servo to set the choke using thermistors  for temp sensing.

Old F

Having so much fun it should be illegal  : )  

[(unknown)]

David Gibson, SL99 co-designer, here.

The SL99 has a high speed counter input. This can be used with a proximity detector to count teeth on a flywheel and translate into rpm.

The SL99 also has an analog input. The range is 0-10V with 8 bit resolution. Input impedance is 200K, so an external 100K resistor would scale it to 15V FS.

FWIW we are about to release an add-on board that will provide 3 channels of AC voltage measurement. Typically this would be used for 3-phase line monitoring. We also have an add-on 5A current transformer.

The SL99 has onboard catch diodes. No physical damage will occur driving relays without diodes. However, we strongly recommend external diodes to combat noise.

                    David Gibson

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[Old F]

Thanks Dave

I am still learning the ropes with it and haveing a blast . The only programming I have done for PLCs has been in ladder

Old F