Project Journals > Oztules

Playing with alternators Part 2

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oztules:
Well the time has come to spend a few hours typing up part 2.

In order to make it easy on me, I'll use up a heap of Wolv's bandwidth and use pictures as much as possible....


We'll start with a sad looking alternator, that I'm not familiar with. It is a little mitsubishi with a diode block I've not dealt with, and enclosed regulator, I've not seen before, and hard to deal with...... and that was just looking in the back of it and going ..... ohhhh dear..

So without further addo, here it is:


And undressed by undoing the three front bolts and gently prying the FRONT off the stator housing:



And seeing into the brush housing



Now a close up of  showing the three small diodes we have spoken off previously. as well as the brush housing.



Here we have released the stator and brush housing and regulator and diode block:



Now we can see the brush pigtails extending from the brush housing itself. It is from here it gets messy:



Here is the underside of the brush housing showing the 4 solder points under it. These solder points go up into the regulator  which is built into the top of the brush housing. This is where it gets a bit confusing for a few moments. Where exactly do the brushes actually go. In this case the brush pigtails disappear into the plastic, and join up with different parts of the alt. One side goes to the regulator, one side makes it's way to the  three small diodes and the ignition input terminal.



We want one to go to the ign terminal, but need to isolate the three small diodes shown here:



So with the usual care and attention, I cut the lot  out and we will rewire for our own purposes. Here the brush housing has been "released" (hacked off from) the diode block:


It shows the three terminals we have access to from the outside world, and the white plate is the backside of the regulator board (SMD components)..... Next step is to destroy the regulator so we can get access to the wires from the brushes, and isolate it all from every where else...


9 images and were out of here....

oztules:
Ok, we have the brush assembly and regulator in our hot little hands, now it's time to do some destructive rebuilding.

By prying off the white plate (circuit board bonded in with strong sticky but hard stuff) I then drilled the wire conduits out that provided the connections to the brush pigtais underneath. In this case, if we put a jumper from one side diametricallt to the other side, we connect one of the brushes to one of the terminals.

These are  the holes we drilled out from the underneath view.  If we join them, it will give us a path from the bottom right  brush point, across to the top left hole which (through the inside of the plastic mould ) goes to one of the terminals. That will give us an external access point to the brush.

 

One of the brushes was damaged, and so we need to replace it from another donor:



The donor came from the black housing bottom left.



Now we just put it back together. Now one brush that went to an outside terminal is still the same but cut off from the small diodes, and the other is joined up to another external access terminal via the jumper we put in where the regulator was.
It is now becoming  more complete. Note the brushes sticking out nicely.....





And now they are not...... They are still there, ..... but thankfully  they provide a pinhole in the back casting to allow you to push a piece of wire in, press the brushes below bore level , and hold them there while you slide the bearing and slip ring assembly back into the housing, as so we don't crash into the brushes.



You can notice the wire sticking out the back of the housing here. This is absolutely necessary with this style of alternator. Normally this type of brush housing setup is for non-internal regulators, but any thing goes I guess. It would be a major replacement problem if the regulator failed in this a style of regulator... (throw away)



Now it is back together. like this.



And this: ... Note the two terminals now marked F1 and F2. They go directly to the two brushes, and both float above everything.... they are isolated but both go to their two slip rings, and we can measure that from the two points.



Now we can see from the first photo, that we have a pulley that is not what I want.... so we simply replace it from another alternator.

.... I wish......

oztules:
The slight problem with this, is that the only other pulleys I had close handy...... well it didn't fit the alternator I am playing with...

Look at this;



Note the sloppy pulley on the shaft. This is not good.



Now I have a lathe, and it would be a simple matter of making a ring to sleeve it..... but that involves work, and other folks don't have this luxury..... so now what.

We only need to hold it concentric until the nut gets done up.... so it's time to cheat.

With a bit of solder, we can stretch it easily to get the diameter that suits us..... This I did, and then wrapped it around the shaft to make a ring  like this:



Time to  place it carefully on the shaft, and check it's dimensions. If it is too big we make another but don't stretch so much. This was a perfect fit ......just luck first time I guess.



Now when we place the new pulley on the shaft, it is a snug fit :



And we now have finished with the conversion..... next we interface with our regulator and we should have what we want.



Note... do the nut tightening BEFORE you reassemble the alternator so you can grab the rotor firmly and give you something to tighten the nut's torque against..... some dill had to disassemble and re do it didn't they.

.........................oztules

oztules:
Ok, now I'm not gonna tell people how to suck eggs. I assume anyone contemplating this can build their own baseplate and mount the alternator and motor in it, so we'll take that as read.

Now all we need to do is put the circuit from Part 1 into a box and connect it to the alternator.

I had a small plastic box from another project, so I used that. I placed an amp meter into it, a 5k potentiometer and the small circuit board holding the parts from part 1

Here we can see the stuff in the box. Meter, pot, and a heatsink on the power transistor, and a heap of silicon goo on the circuit board.  One reason for the goo is waterproofing, but more importantly , is as  vibration protection. This will stop the power transistor moving at a rate greater than the circuit board and heat sink, and fatiguing the legs.


In this one we can see the 1k5 resistor in series with the pot. This is the set value, so when the pot is short circuit to ground, there will still be 1k5 in series with ground on the voltage divider. If we leave this out, then at full power (pot short to ground), the divider point will never get to 7v5 for the zener to conduct, and it output full power at whatever EMF would be dictated by the rpm. It it comes off load in that condition, we nay see hundreds of volts without the battery load, and no voltage control due to the rotor being driven full on. The 1k5 will hold it at around 14.5 (ish) for set and forget after the initial drag has been overcome.



Next I just used a pieces of rubber sheet (knocked off from junk ) to become the back, and a vibration suppressor. It is screwed straight into the plastic box from the rear
.

So now it looks like this:



The regulator control cable is fed back through the rubber and goes to the alternator. I used power cable from an appliance (form the tip) and it's colours are blue, brown and green/yellow.



I used the brown for the B+, the blue for the B- and green/yellow for the regulator control voltage. So the red goes to b+ on the back of the alt, the blue goes to ground on the alt, and the green/yellow to any our of our two spade terminals sticking out the back of the alternator.

A separate red wire goes from the b+ straight to the other terminal attached to the brushes.


Here the blue is grounded as is the negative take off to the battery, the brown to b+ terminal, The input to the amp meter for power out is on the b+ as well



Only the green to attach to the second brush terminal, and we are wired up.



The output wire from the amp meter goes to a stud on the rubber and then off to the battery...... and were done.



We now have one fully controllable generator set.

...................oztules

Notes and other waffle:
1. A fuse in line with the battery leads will protect both the alt and the controller. If the battery is reverse connected, the very high surge ratings of the diodes will blow the fuse before diode damage if it is sized reasonably close to max output.

2. The blue, brown and green/y wires in the pics are connected to the circuit board as brown=b+ blue is batt- and green is output from the control circuit.

3. The alternator in this final part is not the one in the first section.... it will go on another motor as a 24v unit. The voltage divider will be altered to different values and we will test it over a few hours of running to see if the 12v rotor qill be ok..... I'm sure it will, but seeing is believing.

Questions, comments and corrections welcome as always. :o

Wolvenar:
Glad you used that alternator for showing this process, Chrysler has been using that style of Mitsubishi here in the states for decades now.
This should help make it easier.

Great write ups so far.

Thank You for sharing.

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