RR45 Notes

This gizmo 'ere:

As for yer basic BMW 280W 3-phase alternator with self-excitation rotor, (big-block Tontis and R-series BMW twins).

Been trying to get my head around how the orange wire works, in fact how any of it works really so yesterday afternoon I put it on a power supply to find out. At this stage this power supply merely represented a battery, and as it happened that’s all I needed to do…

The instructions say “The RR45 must ‘sense’ a threshold current of 120mA down the ORANGE wire before it will wake up from rest and go” ~ yes true ~ sort of.

I didn’t measure 120mA but instead 63mA, and as far as I can tell it is a constant current source.

So, where the instructions then say you can use the dash panel warning lamp bulb with the orange wire, and that a 1.2W bulb is not ‘big’ enough, it turns out it will, in this case (63mA), light up, if dimly. Where it then says a 3W bulb is ‘too much’ and won’t light up, so a 2W bulb is recommended, that too will be ‘too much’ and not light up! (In this example I’ve got here.)

In all cases though the regulator is definitely turned on, even by a 1.2W bulb.

What happens then is, DC current goes out the rotor output wire (brown) straightaway, i.e. it’s getting it directly from the ‘battery’. (No AC input at all on the yellow stator wires for this demonstration.)

So, it seems what we have here is, if you like, 2 ‘separate’ parts ~

#1. a 6-diode rectifier block, for 3-phase AC to battery (only).

#2. a regulator that runs directly off the battery Voltage.

If so then the internal block diagram shown here (inset) is not very accurate (because it implies rotor current comes from the stator via 3 extra diodes only when it’s running):

It’s worth knowing though that as soon as the ignition is turned on there’ll be 4 Amps going to the rotor immediately from the battery, add to that say another 4 Amps (typically) for the ignition system you’ve got 8 Amps on the go already before you press the starter. I was going to connect the orange wire via the kill switch anyway, and I’m now more convinced this is a good idea.

Still not sure how the orange wire constant current source / start-up switch works, without going into some complex circuitry (entirely imagined), as there isn’t a lot of room at all in the resin block in which it all lives, so I’m not sure how sophisticated it really is. On the other hand, surface mount devices are a distinct possibility, allowing maximum miniaturisation. Could even be an integrated circuit in there.

I’m guessing the rotor output will turn off if the ‘battery’ Voltage is raised by an appropriate amount, but haven’t tried it yet.

Some sophisticated regulator circuits involve an oscillator to switch the rotor with a variable mark-space ratio, but the simplest method is merely to monitor the output Voltage and switch according to that.

Still scratching my head how to make the dashboard bulb work efficiently…

Good stuff Mike! Reckon this should be a sticky in the Non-OEM section

I will copy the page and add it in the non oem section


Ta peeps, Ok more info.

There is a constant leakage current of 290 uA from the battery while it’s connected and in the ‘off’ state. I.e. there’s some sort of circuit constantly being powered all the time the battery is connected. It’s quite feasible that this 290 uA is the bias to make the orange wire current source work (simple scenario), but that’s pure conjecture. Seems perfectly reasonable though that something is sitting there waiting for the orange wire to go positve.

While in working mode, (orange wire to +12V) it turns out that raising the ‘battery’ Voltage does not cause the rotor output to change.

Right then, so in fact it does actually ‘look at’ a second rectified alternator output to sense the Voltage level. Fairy nuff.

This means 9 diodes (i.e. as per original Bosch rectifier configuration), to get the second rectified output, not 6 as I first thought.

An extension of this realisation was that I then, on a whim, tried a diode test from one of the yellow wires to the orange wire, and got 1.2 Volts, this suggests to me 2 diodes in series.

The test was unambiguous so the implication is that a diode connects rectified alternator output #2 to the orange wire.

In other words, exactly the same as the standard Bosch system where the bottom end of your dashboard bulb connects to the point between rectifier and (electro-mechanical) regulator. So, when the alternator produces Voltage at this point (which will be virtually identical to what’s on the battery) this diode becomes forward conductive and ‘takes over’ the orange wire current from the dash bulb (if used) so that the bulb goes out. (Zero Volts across it.) Actually if I was designing it, that’s how I’d do it as well, as it’s the simplest way.

Theoretical spice simulation schematic to follow…


This is an Electrex Regulator rectifier as my pal just fitted. Interested to know how are getting on with your charging light, as his is a wee bit dim.

love and kisses

Do you know what this might be an integrated circuit, I’ve just found a bunch of data sheets for the L9000 series automotive regulator chips (well some them are).

These features leap out:

Positive output for ground side rotor (= other end is connected to ground / chassis / frame)

Stand-by current: 300uA.

L Terminal Regulator Activate Threshold (0.8 - 1.15V)

The ‘L terminal’ is the lamp terminal.

The lamp terminal is current limited. When the alternator is running it goes positive and may then be used to operate a relay. A-ha!

Application diagram from datasheet:

And it looks like:

Its ‘footprint’ is about 20mm square so should fit in.

Tell me about it.

I am still thinking…

I have this fitted to my T3, the old type with definitely no charging light, and I went and bought it directly (some years ago now) from Peter Houghton, the boss at Electrex UK, as I was doing an article for CB mag on him. He’s very nice, and very approachable, and I’m sure he wouldn’t have a problem on letting on how all this electro-wizardry works if required. I remember chatting to him about electronic ignition for Guzzis and he was interested in using my bike as a possible ‘muletto’ to try out various solutions using digital technology - but it didn’t really go any further than that.

You’ll like this Mike - here’s a pic I took of him at his bench in his R&D zone. I could only recognise a soldering iron…

Very interesting, thanks!

Actually the more I think about it the more I’m convinced it’s one of these L9xxx chips, if only because there’s only enough room inside the case (black epoxy block part) for one of these and six diodes, problee on a bit of a board, would be impossible to shoehorn anything else in.

Seems you can get these in America (at least) quite easily, I found 9466, 9573 & 9484 are stocked by Digikey.

As to the dash lamp problem, best idea so far is a reed relay …

Need to do some sperrymints …

Appendix ~ just FYI, I note the chip has thermal shutdown at about 175 ±15 °C ~ that’s junction temp so if steam comes off when you spit on it it’s problee getting a bit too 'ot for comfort…

Mike H2012-09-06 20:24:27

OK using my homemade reed relay to operate the lamp doesn’t work.

I am trying to find a simple way of lighting the lamp more efficiently, and not succeeding.

Anyway here’s a better drawn (IMO) application diagram from L9911 datasheet (the fourth one I found):

The chips are made by ST Microelectronics. The internal circuit is doubtless very complex. No internal schematics can be found on the web, not surprising really (copyright etc.). We’ve established that the stand-by current (off state) is <= 300uA, and is a continuous current drain on the battery. Which is not at all huge, amounts to 3.6 milliwatts. A dash clock will be more significant than that.

Using the simplest version as an example (L9466) the device is activated by raising the lamp terminal pin to >= 1V. It then turns on the field rotor. (Or at least it turns on my dummy load resistor on the ‘test bench’.) It then waits for alternator activity by looking at the ‘P’ pin, which is connected to one of the stator phases. (Which I can’t simulate, I don’t think.)

Once it’s got this, the lamp terminal is switched high and, once the alternator is running on load, the rotor is switched on and off at maybe several hundred times per second, with a variable mark-space ratio. Which means the ‘on’ time versus ‘off’ time are altered to vary the mean average rotor current (aka pulse-width modulation). That means it has an internal oscillator but how that is done without external timing components I’ve no idea, unless it’s high frequency and divided down and manipulated digitally, which is quite plausible.

The set Voltage is around 14V, but does depend on chip temperature, so, at 25°C it may be up near 15V (this has come up on one of the BMW forums [fora?] as “this is not good enough”), but you have to assume that subsequently the chip heats up so at 70°C it should drop to around ±14V. At 150°C it could be down to 13.5.

By the way did you know rectifier diodes get hot too, I make a very rough estimate of 1 Watt per Ampere for each diode (x 6 of them). But due to 3-phase, only 4 of them being on at any one time on average.

The dim lamp syndrome (also as noted by theone&onlymin above) looks like it may be a frequent problem, and I think I’ve noticed same sort of queries on a couple of the BMW forums. (Fora?) I might resort to trying my original ‘plan A’ which was to get it to work a low-power relay and have that switch the lamp instead. The current I’m getting out of the orange wire is certainly not what the Electrex sheet says.

First need to fix my DMM again, the LCD is losing segments (again) due to ‘dirty’ PCB pads so needs an outing for the switch cleaner and cotton buds at some point.

Later dudes…

The saga continues…

Experimented today with a low power 12V relay (plan ‘A’ resurrected) and got it to work. Though needs a shunt resistor to get the current right for the regulator chip at pin 2 ~ it seems the actual current is not critical, but the device must ‘see’ 1 Volt or higher on this pin. Although my example will work on about 0.65V, so go figure.

Anyway here’s my spice simulation of it (version 4, not involving transistors [for a change ]):

It works because this particular relay will operate at quite low Volts, around 7.5 at least, but note the shunt resistor value may have to be ‘tweaked’ as necessary with a similar type of relay and depending on the actual chip current you may have. (Mine measures as 64 mA.) Rather down to ‘try it and see’ I’m afraid.

‘Waveforms’ of simulation ~ green: pin 2 Voltage (‘ignition’ on at 1 sec); pink: lamp current (1.2W bulb):

I found what I think is a close match for the relay at the RS web site here:


Wired as follows, pretty much ~ I was thinking of just soldering small gauge stranded wires onto the PCB pins and sleeving them.

Need to dig the instrument console out of the shed and see about fitting it in somewhere.


Didn’t they use that method on the Turbo Encabulator?

Ey up me web site’s back online.

Aye but you also need to sprinkle it with magic dust No. 15

Forgot to mention that