Dynastart regulator.

[piratepaul]

I have been asked to make a regulator for a dynastart.

It must switch off if the voltage goes above a certain level, I think that was supposed to be 16v I am thinking 15v would be safer.

It must switch off if the dynastart voltage drops below the battery voltage or the dynastart will power the engine at low revs...thus flattering the battery. I am thinking of setting that at about 13v.

It must switch off if the charging current goes above 20A.

I am thinking of monitoring the dynastart voltage with an A/D converter and the ampmeter resistor voltage with an A/D converter. Setting up a combinational logic circuit to switch a big transistor ( cut off transistor).

Any suggestions welcome.

[piratepaul]

And a secondary circuit with solonoid to start the engine.

[piratepaul]

I might need 3 A/D converters so I can monitor the dynastart and battery separately.

There could be a problem because when the engine is running at high revs and the transistor is switched off, the open circuit voltage of the dynastart will be high. If I switch the transistor there will be a high voltage pulse which will drop quickly, but not necessarily quick enough so as not to do damage. So I need a way to introduce the dynastart slowly, a dummy load or etc or etc. A choke or?

Any bright ideas?

[piratepaul]

Options.

I could perhaps use a relay instead of a big transistor, switch the relay with a small transistor.

I could use a blocking diode to prevent reverse flow at low revs.

I could put a big cap between earth and the battery side of the big transistor and a choke between the cap and battery on the positive side. What spec cap and choke?

May be switch on a dump load to drop the dynastart voltage to less than 15v, then switch the dump load off and simultaneously switch the transistor on, so the voltage applied to the batt ( and fuse box (boat)) goes from low to high, rather than high to low. Perhaps 555s or opamps switching the dumpload on every few seconds to sample dynastart voltage so as not to leave the dump load on and waste power. The dump load only switches on when the transistor is off.

May be tap a voltage from a dump load pot, then switch if of and simultaneously switch on a different pot etc.

[Richard]

I just googled "dynastart regulator" and found several sites offering modern electronic regulators. Perhaps a bit more expensive than what you had in mind, but when you factor in your time probably not so bad after all ...

[piratepaul]

Why didn't I think of that.

I will tell him next time I see him.

Tar&stuff