The Great KB Regulator & Rectifier project.

[davereid]

OK, I'll design something today, should have something on-line for the builders today or tomorrow.

[davereid]

OK... attached a circuit diagram, and the manual for the IC.

[Warr]

Sweet.Will likely find a diode array out or a tired car alternator ...
What frequency have you set it to run at...
How come no inductor in output ??

[davereid]

It should run about 2khz.

No inductor required as we are are not filtering the output, the battery can do that for us, so we can use a slower oscillator than might otherwise be selected. This is kind on our transistors, and might help constructors, as they should be able to hear it grunt up.

The error amplifiers have been turned into comparators with hysteresis, this is also to reduce the workload. The result should be a system which switches in-and-out, commencing charging whe the battery drops below 12.6 volts, and charging up to 14 before reducing charge current.

The current limiting should be set to avoid damaging the output transistors. By default it will also stop the battery loading the charging system while cranking.

[pete376403]

Would veroboard tracks be adequate for this?

[davereid]

Would veroboard tracks be adequate for this?

Yep, for everything except the transistors and rectifier.

DB pointed out that if you were to turn the key off, while coasting in gear, the regulator would lose its feedback, and would stop regulating.

It may not do any harm, as the current limit would still work, and the bike will soon stop, but well spotted Steve.

No doubt a few more bugs in there yet !

I suggest as a fix, pin 12 of TL494 be connected to the battery via the IGN SW instead of to the rectifier output.

[Warr]

It should run about 2khz.

No inductor required as we are are not filtering the output, the battery can do that for us, so we can use a slower oscillator than might otherwise be selected. This is kind on our transistors, and might help constructors, as they should be able to hear it grunt up.

Could this be asking too much of the battery. My thoughts are for the solid state ignition systems we all run. I realise a suitable inductor may not be a straight-forward bit of kit to buy but would be relatively easy to build.
... I'm no expert but just asking tis all.

.......
The current limiting should be set to avoid damaging the output transistors. By default it will also stop the battery loading the charging system while cranking.

What max charge current would you suggest ?

Do we know what the input voltage would rise to when the regulator is in "off mode" ? Will the 1000uF input capacitor be high enough rated at 63volts ?

[notme]

Could this be asking too much of the battery. My thoughts are for the solid state ignition systems we all run. I realise a suitable inductor may not be a straight-forward bit of kit to buy but would be relatively easy to build.
... I'm no expert but just asking tis all.


What max charge current would you suggest ?

Do we know what the input voltage would rise to when the regulator is in "off mode" ? Will the 1000uF input capacitor be high enough rated at 63volts ?

Your battery is already doing this job in your current charging system - it wll be fine. It's just doing what it does in it's function as an energy storage device.

Max charge current will be a hard one to specify as it depends on your consruction i.e. heatsinking and mounting, and your bike's electrics and battery size. You probably want to measure your bike's current draw at full load (all electrics on, headlights on high etc) at idle and at a few points in the rev range, and go from there. You want the current limit to be higher than the max current that the bike wants at any time.

Also - check the diodes you use for the rectifier bridge, 50Hz ones are probably a bit slow as I think most multipole alternators spit out AC at up to a KHz or so - would need to check this for your bike though.

[davereid]

Could this be asking too much of the battery. My thoughts are for the solid state ignition systems we all run. I realise a suitable inductor may not be a straight-forward bit of kit to buy but would be relatively easy to build.
... I'm no expert but just asking tis all.


What max charge current would you suggest ?

Do we know what the input voltage would rise to when the regulator is in "off mode" ? Will the 1000uF input capacitor be high enough rated at 63volts ?

The battery should cope - it will make a fine filter !

I guessed at the alternators peak output as being 30 - 32 volts - 2.5x the nominal load voltage.

Maybe I am a bit off track here ? Should we allow for higher alternator voltages ? What do they really output - anyone measured one ?

[jonbuoy]

Standard bridge rectifier diodes will be sweet - Also as its an AC generator won't the output voltage from the stator stay the same regardless of engine RPM - only the frequency of the cycles will increase?

Edit: Also on the circuit you've got up, the voltage at the input to the controller could be higher than 42VDC - the guys on the blade forum measured 45VAC off load on the stator -that will be even higher when its rectified into DC. And it will surely be messy, maybe you could take the supply further down from the battery itself? I don't think its going to work very well - it would be fine if the output of the rectifier was proper DC but it won't be if you scope it'll still look pretty messy - a big cap might help but then its a pain to fit.

[pete376403]

Not sure if this is relevant, but the test process for GS Suzuki stator says the stator is bad if the voltage between any pair of stator leads is less than 60V AC at 5000 RPM.
I know on my bike I've seen about 75VAC when doing this test.

http://thegsresources.com/garage/gs_statorfault.htm

[davereid]

Not sure if this is relevant, but the test process for GS Suzuki stator says the stator is bad if the voltage between any pair of stator leads is less than 60V AC at 5000 RPM.
I know on my bike I've seen about 75VAC when doing this test.

http://thegsresources.com/garage/gs_statorfault.htm

Good link.. a couple of minor mods required to handle the extra voltage, and jonbuoys concern about the power supply uses the same fix as DBs question.

I'll re-draw and re-post the diagram with the mods done.

Beer required first.. !

[davereid]

OK, revised as follows..

Power supply (and soft start circuit) now also switched and supplied via keyswitch.

MJE340 transistor added to allow 100-140 volts plus voltages.

Capacitor upgraded to 100v - or just use the voltage you need.

[notme]

Standard bridge rectifier diodes will be sweet

Diodes - standard (i.e. slow) diodes will not be OK on a high frequency system, unless you don't mind wasting power in them.

Also as its an AC generator won't the output voltage from the stator stay the same regardless of engine RPM - only the frequency of the cycles will increase?

The type of alternator in most bikes is a low rpm permanent magnet alternator - unlike a high rpm car one with an adjustable stator field.

What this means is that as the engine RPM changes, the output frequency and power of the alternator changes with it. It's actually a fine balance between having enough charging power at idle to ensure that with ful load you don't run out of juice if you sit idling for 15 mins and making sure you don't generate a bazillion watts of power at high rpm. All of this is solved with a car style alternator but as previously mentioned the complexity and costs are keeping them out of bikes at the moment.

So the voltage AND the frequency of the ripple on the alternator output will vary with engine RPM and load.

Edit: Also on the circuit you've got up, the voltage at the input to the controller could be higher than 42VDC - the guys on the blade forum measured 45VAC off load on the stator -that will be even higher when its rectified into DC. And it will surely be messy, maybe you could take the supply further down from the battery itself?

Not sure what you mean here? You could take the supply for the chip from the battery, but then if the battery is flat the chip will not enable the charging system e.g. if you push start the bike. Also unless you add more complexity with a shutdown circuit the chip will draw power from the batttery while the bike is off. It could all be done, but Dave has designed in a nice simple solution and the cap size given will be plenty, as the chip is not drawing huge amounts of current.

I don't think its going to work very well - it would be fine if the output of the rectifier was proper DC but it won't be if you scope it'll still look pretty messy - a big cap might help but then its a pain to fit.

You might be surprised how close to "DC" the output is! It's not battery like, but it's not exactly swinging up and down by 30V. Older style mains powered automotive battery chargers used to just have thyristors that would allow continuous pulses of rectified AC going from 0 to ~14V to charge a battery.

HTH

EDIT: Dave has been drawing while I composed my thoughts - chip power supply issue fixed! :-) Another potential improvement is to filter the chip suppl via some series impedance, meaning the cap will have more effect.

[Ixion]

Hm. Will this work on single phase alternators (with two less rectifier diodes of course)? Most of my bikes are so old that multiphase hadn't been invented.