Need help in undestanding a rectifier.

[yshtar]

I need help in understanding a rectifier to charge a lead acid battery on my bike. I checked it with an ohm meter to see where the current flowed, like this:

--- I put the positive on Pin 1 and the negatives on Pin 2, 3, and 4 and they connected. So, the current goes from Pin 1 to Pin 2, 3 and 4. (Am I right?)

--- Positive on Pin 2, the current goes to Pin 4.
--- Positive on Pin 3, the current goes to Pin 4.

Now Pin 1 is connected to the positive on the battery, and Pin 4 to the negative.
One end of the pulse generator is connected to Pin 4 (and the negative of the battery), and the other end is connected to Pin 2 (or Pin 3, since they have the same direction).

From what I understand, the positive charge should go out from Pin 4, and it should be connected to the positive of the battery, and Pin 1 to the negative of the battery. But when I did it, the battery lost power.
I checked with the DC volt meter, and placed the positive pin on Pin 1 and I got about one volt, so the current seemed to go out from Pin 1.

Any help will be appreciated. Very confused here.Thanks in advance.

 

[yshtar]

Well, I've found out the problem. I did it with analog meter, and an article I just read said that the Black pin is positive and the Red one is negative when measuring. It solves the problem, and now I know how to connect the wires.

Thanks a lot, folks.:)

 

[KingNothing]

Well, I am confused too. Especially by this statement:

--- I put the positive on Pin 1 and the negatives on Pin 2, 3, and 4 and they connected. So, the current goes from Pin 1 to Pin 2, 3 and 4. (Am I right?)

You are using an ohm-meter to try to read currents? Generally speaking, an ohm-meter is not something you use in-circuit. It's really only useful to measure the DC resistance of a single component on its own.

 

[sophiecentaur]

Well, I am confused too. Especially by this statement: You are using an ohm-meter to try to read currents? Generally speaking, an ohm-meter is not something you use in-circuit. It's really only useful to measure the DC resistance of a single component on its own.

You can 'do' diodes perfectly well with an ohm meter - after all, you want to know the resistance in two directions, don't you?

@yshtar
You have four terminals on your rectifier block so I assume it is a bridge rectifier (?). Either look up the device number on the internet and find how to connect it or: Look for two pins with a, AC symbol (an S on its side) between them. Connect your input either way round across these two. Look for two diode sympbols on the other two terminals. The 'arrow out' or + symbol should feed the + battery terminal and the 'arrow in' or - symbol should feed the - battery terminal. That way the battery will charge on both halves of the AC cycle if you are using an alternator. You have a meter so it would verify that it is working right. Have you got the right voltage from your alternator?

 

[yshtar]

Thanks to all.

It's a half wave rectifier, and it seems that Pin 4 is the one I should connect to the pulse generator, and the other end to the negative of the battery, while Pin 1, 2, and 3 is the outputs. It's a motorcycle's half wave rectifier.

Now I have another problem with it again. See, I use the pulse generator to turn on the headlight and charge the battery. The rectifier's fine, no leak, no short, and it charges the battery well, but when I turn on the headlight the battery starts losing power quickly.

The wiring is like this:

The pulse generator's first end (A) goes to the headlight, and it's branched to the rectifier input line, and the rectifier's output line goes to the positive of the battery (connected to the positive wires).
The other end of the generator (B) goes to the headlight, and it's branched to the negative of the battery (connected to the ground/negative wires).

It charges the battery well, and there's no problem if I don't turn on the headlight. If I turn on the headlight, the battery losing power quickly. I don't understand this, because the rectifier doesn't leak. What should I do? I've checked everything and found no short.

 

[sophiecentaur]

A half wave rectifier is, surely, just a diode. What could the other terminals be for?
I might suggest that the lights are draining the battery because it's not been wired in correctly.
Or the pulse generator has not enough current output to support the lights. Does it work when connected to the bike generator?
Edit - what does your current meter tell you about the current that you are charging the battery with and about the drain with the lamps?

 

[yshtar]

There seems to be 5 diodes in the rectifier, with 3 outputs. If this is what you mean with "terminals," one is for the headlight, one might be for patrol and others. I've modified it.

I'm suspecting a short or some kind, but I really haven't found any. I'm going to rewire the ones going to the switches, since it's the only chance left.

The pulse generator I meant is the bike's, and everything works fine. And I'm sure it has enough power for the battery and the lights, since I ever give the light a diode and it was still bright, though not smooth when the engine running low.

Thanks, btw. I'll be back after I finish rewiring.

 

[yshtar]

Well, I am confused too. Especially by this statement:


You are using an ohm-meter to try to read currents? Generally speaking, an ohm-meter is not something you use in-circuit. It's really only useful to measure the DC resistance of a single component on its own.

Sorry I forgot it.
Yes, I use the ohm meter to check the diodes. It's the only one that uses current, right? We can see if the diodes ok or not with it.

 

[sophiecentaur]

Ahh, I see. Although 5 diodes and three outputs still sounds like more than a simple half wave rectifier. It sounds more like a full wave system.
Well, if you have (or are supposed to have) a diode in series with the headlights and a separate diode for the battery, the battery shouldn't 'see' the headlights at all. If the system is that simple, why not just rewire with individual diodes ('fanning outwards' from the generator output)? At least you'd know what it was supposed to be doing.
Does your meter confirm the way the diodes in the block are / should be working?
Have you ever drawn out a circuit diagram for yourself? It would be interesting if you could post it.

 

[yshtar]

That's a nice idea! But I'll give the headlight a diode if the problem persists, because I want it to have full wave. I'll try giving it to the positive wire from the battery first. Besides, the diode sold around here fried when I put it on the headlights. Very low reverse voltage, I think.Thanks.:)

You mean the diagram of the rectifier? Yes, it's simple, but confusing at first. I'll try drawing it and post it when I can. I haven't done it with the pc. Not sure what program I must use. lol.

Thanks again.:)

 

[sophiecentaur]

A pretty naff diode,I must say. Most diodes will handle -15V with no trouble!
But the diode needs to be against flow from the battery to the lamps. Putting it in series with the lamps will make no difference (unless it actually stops any current from any source, flowing through the lamps. The lamps need to be 'upstream' of a diode in series with the battery. Your lamps will LOVE an AC source (direct from the generator).
Like I said- a circuit diagram would solve a lot of these unknown problems

 

[sophiecentaur]

You mean the diagram of the rectifier? Yes, it's simple, but confusing at first. I'll try drawing it and post it when I can. I haven't done it with the pc. Not sure what program I must use. lol.

Thanks again.:)

I meant a diagram of the whole circuit - including any ground connections. I think there is something missing in what you have seen or described.
Draw it on paper and take a photo??

 

[AlephZero]

Besides, the diode sold around here fried when I put it on the headlights. Very low reverse voltage, I think.Thanks.:)

A pretty naff diode,I must say. Most diodes will handle -15V with no trouble!

More likely, the diode had a forward current rating that was too low.

Assuming motorbike headlamps are similair to cars, they probably use 55W bulbs which take up to 5 amps current from a 12V battery.

If you used a small diode rated at 1A continuous current, it might work for a short time (a minute or two) but it wouldn't be reliable for real use.

 

[yshtar]

Ok, I just drew it. I hope it's clear enough. The tail light also represents the others, the sign, brake, and horn. But I haven't checked if the battery losing power with the tail light off.

I used the 6 amp diodes. It became very hot in a few minutes, so I made a parallel of 20 diodes to ease the current and reduce the heat, and many still fried after a few days.

Btw, the generator pulse produces about 40 volts AC when roared. Not sure about the amp, I have no amp meter.
And I use a 100 watt bulb.

 

[sophiecentaur]

I have a lot of questions / comments. Please bear with me and read them.
Are those little arrows on the wires current direction? The diodes would be the arrows with the bar across, i guess.
I am a bit confused about what "first cycle" and "second cycle" refer too - as the switch is in different positions for each picture. The circuit describes itself - without needing to show what happens on each half of the cycle; the current arrows are superfluous - or worse.
There seems to be only one diode that is actually operational in the block. Strange.
There appears to be no path on the diagram for current to flow from the battery around the headlamp so I think there is something seriously wrong if, in fact, the battery is discharging through that lamp.


I can't believe that the circuit arrangement you have drawn is as it should be. You may have inherited some 'modifications' by someone who didn't know what they were doing??
The diode block is weird - it seems to have two series diodes in parallel with one diode. Are they normal diodes?
What is your reason for thinking that it is supposed to be just a half wave rectifier? You appear to have enough diodes for a bridge rectifier which would make much more sense. It would only require a slightly different way of connecting them. Are you really really really sure that you have what you think you have?
What are the volts across the bulb when switched on and the engine turning at a reasonable speed? This is relevant because a bridge / fullwave rectifier will give you twice the volts of a half wave rectifier. SO you may just not have enough volts to be charging your battery with your circuit when under load (the generator may have been designed with a bridge rectifier in mind). The tail light would be draining it when the headlight is on.
One last question - does the generator get hot when the headlights are on?

 

[yshtar]

It's ok. And I apologize for the arrows. lol. I'm used to it on the lines.

The first and second cycle, wrong wording, sorry. Maybe first half and second half are the correct ones.
And I also drew the "second cycle" to show the currents.

The modification I know was the one I made when I changed the windings, and this was what made me asked the first question. I've been checking the wires today and it seems that the factory didn't use normal wiring. It seems to be reversed somewhere along the way. I've found the tail light wire on the switch was the ground wire, not positive as it should be. And from what you said here, it seems that you also see no problem with the currents in every direction, so I will focus on the wiring.

The rectifier, I think they're normal diodes inside, and I think it's half wave since there's only one input line on it. I've never opened it, but I know how it works. The first output goes to the headlight, the second goes to other lights, the third goes straight to the battery. If the headlight and/or other lights are not turned on, all the power goes to the battery. It's how it works.

The generator, there's only wires inside. I know it since I did it myself. lol. I haven't checked the volts with the bulb on, but I've checked it directly and when the machine roared, the peak is about 40 volts.

The last question, I can't tell. The generator's inside the machine block, so I can't check it.

Btw, I don't mind being asked lots of question, as I myself ask a lot. :)

 

[sophiecentaur]

Hi again.
some more questions:
If you haven't looked inside the block then how do you know what's inside? Is there some documentation with it?

Headlights don't need rectification so, as the diagram shows, they are fed directly off the coil. With no load on it, the coil could have (and does have) loads of volts but that's pretty irrelevant. What counts is the volts it can supply under load. You would normally expect to have enough output for the generator to just charge the battery when running at tickover (even with the lights on). This means that it just could be essential to use a bridge rectifier circuit as it gives twice the dc volts. I assume that you wound the coil with as many turns as possible of the original gauge of wire (?) so it should work as it would have done originally and supply the right volts for the original design.
I remember having a BSA Bantam (150cc) in 1966 (it was ancient when I bought it too) and the battery terminals became disconnected and the sidelight / backlight filaments all burned out as the volts soared way above the required 6V.

You seem not to be picking up on my comments about the diode block and how I think it is dodgy in some way (not how I would have ever done it because the design appears to be a bit 'nonsensical'. If we were dealing with a simple half wave rectifier then all we should have is one fat diode - not this odd network of diodes. Neither head or side light need DC. Are they encapsulated totally or are they soldered to tags inside a block? Could the arrangement have been tampered with? Any chance of a photo and or a component number?

Could you borrow an ammeter from somewhere to find how much the battery is actually charging?
I really want to get this thing working now!

 

[yshtar]

The block? If it's the rectifier, I checked the directions of the current and drew it. And if it's the generator, the coil, because I did the winding.

And the current headlight doesn't need rectification, because I made it so. Originally it used the second (middle) terminal.
I will check the volts again when I've done the wires and switches. And yes, I did wind as many turns as possible to get the most of it, and I killed several bulbs because of it.

And I don't understand "not to be picking up on my comments..." Would you please elaborate? I'm not of english speaking country. I read well enough, but I guess many times, just like what I do with "elaborate." I'm not really sure of what it means, but I feel that it's used to ask someone to explain.:)
I just asked a friend, and she said that "you seem to be not to be picking up..." is something like "you don't understand..." Well, I was not sure of what you meant. I kinda understood it, but I worried it wouldn't fit this forum to talk about what I think of it. But since you asked, ok. I think the same as you, that I could make a bridge rectifier with double power with it. It's messy, especially with the 2 other terminals that function to change the color of the wire. I'm sure of it after I checked the wires connected to them and where they come and go. Plus, the factory original input was through the ground wire which is not normal. And I think the factory made it this way to confuse people, so common people would buy the factory wiring and rectifier.

I can write a lot about what I think of the rectifier and wiring, since it's confused me for days, but I better end it here. lol.

Thanks for helping me, Sophie.:)

 

[yshtar]

Sorry I forgot it.

"I remember having a BSA Bantam (150cc) in 1966 (it was ancient when I bought it too) and the battery terminals became disconnected and the sidelight / backlight filaments all burned out as the volts soared way above the required 6V."

It happened if the battery was disconnected. I used to do it to brighten the headlight.


"I assume that you wound the coil with as many turns as possible of the original gauge of wire (?) so it should work as it would have done originally and supply the right volts for the original design."

The volts I now get from the coil surely is lower than the original since I used bigger wire to get more power (amp). I think I used 1.1mm wire, so it must be less turn in there.


"Could you borrow an ammeter from somewhere to find how much the battery is actually charging?"

I don't know where to find it. So far my reference is the size of the wire (of the winding), and I don't remember it. I had a book that mentioned the amp one size of wire produced.

 

[sophiecentaur]

Re "picking up comments". Yes, it was a kinder way of saying that I don't think you understand the significance of the bridge rectifier problem.
If you have wound the coil to match the original then it should be doing what the last one did so that's out of the area of worries, I think. It should be something like the original, though. It's not just the volts that count, you know. Ideally, the winding should be designed as a compromise between getting enough volts with as few turns as possible - so the wire can be thick enough to deliver the current without getting too hot. It's a matter of Matching the generator to the load requirements. Did you use the same gauge of wire - or just chose a gauge and piled as much in as you could.LOL.

There is no particular significance in having a Negative or Positive Ground. Most modern vehicles use a negative earth, though. It would be better for you to have a Negative Ground if you want to add 'modern' electronic equipment.

So tell me about this diode block. You deduced the set up by measuring resistance in both directions between the terminals? Fair enough
Are you sure that the original coil was not centre tapped? That block would imply something of the sort. How old is the bike? What make?

 

[yshtar]

lol. I really did pile as much as I could. lol.
And I had to alter the windings a bit. There were 4 in there, one for the spark plug, and the other 3 for the lights and battery. But 3 windings of that 1.1mm wire killed several 100 watt bulbs, and after I paralleled several bulbs totaling 160 watts without any being killed, I separated one winding for the battery and later I added 100 watt H3 bulb, after killing a few 55 watt bulbs. lol. and this one is the one having problem. The other 2 windings I use for a 100 watt H4 bulb.

That was what I did with the rectifier. And I don't think it's a center tapped coil, since the current flow of the rectifier doesn't match the center tapped rectifier. And the rectifier also have only one input line, while the center taped rectifier has 2.

It's a 1987 Honda, and it may not exist there. I'm from Indonesia, btw.

 

[yshtar]

Sorry I forgot it again. I have 8 windows opened here. lol.

The wire, I had a book that mentioned the amp one gauge (size) of wire produced. It was a junior high book, I think. I bought it when I decided to wind the coil myself. It was done twice by other people three times. The first got burned, and the second and third couldn't give enough power for my 100 watt bulb. They used 0.9mm wire, so I thought I'd need to know the amp the wire produced and I chose 1.1mm. Later when I took the coil out I found out that it was not wound fully, and it also was uneven. But as I bought the 1.1mm already, I used it still. Never thought I'd have to buy several bulbs because of it. Really, as each winding can handle a 100 watt bulb, I can have 3 headlights with 100 watt bulb turned on each at the same time. lol

 

[sophiecentaur]

Sorry to keep on about this but, if they're not for a more complicated rectification system, what are all those diodes in there for? We agree that the only reason to have a rectifier is for the battery and for electronic equipment. If you haven't any record of the original system then what evidence do you have that a simple half wave rectifier is all that was intended?
I think you may be in a better position to know what you need once you have measured the volts under load and also measured the charging current to the battery with and without the rear light connected and for varying revs.
I do think that you may need to consider winding another coil with a more appropriate spec. Is that too much of a pain to contemplate?

 

[sophiecentaur]

I seem to remember my bike had coils wound round radial 'spokes' of a laminated iron ''web' that the flywheel rotated round. Is yours like that? That arrangement could well be a multiphase system - giving a very smooth output when rectified. A photo of the various bits would help a lot. I have seen various images on Google that look familiar in construction.
Your problem is that there are no bike repairers who are prepared to do anything more than replace bits these days and they will just sell you a totally new or re-con part.

 

[yshtar]

Sorry I'm late. I felt tired thinking of the bike yesterday. lol
And it's ok to ask, at least for me. :)

Probably all the motorcycle here uses that kind of rectifier, no matter what the make is. I know it's a half wave rectifier from the single input and output, since the bridge and center tapped rectifier have 2 inputs. And I remember that one wire form the rectifier went to the headlight.

I've checked the volts under load (battery), and it's 2 volts at idle, 18 volts roared, and about 25 volts top. Do you think it's enough? It did charge the battery well, but now I'm thinking of opening the rectifier and build a bridge system with it. Btw, it's encapsulated, and the numbers gone. And I can't take a picture. I only have a cellphone cam and it's no good.

And the original coil was like: first winding-> turn left, second -> turn right, and third winding -turn left. I had to figure it out since 2 guys did the winding before, but since there was only 2 wires went out of it, I'm sure I did the right thing. I wound it it that way before I decided to separate the second winding.

Btw, I'm not sure about the charging current, but it went over 10 volts.Sorry I forgot it. The coil here, it's like + sign in a circle. The + is the iron, and the circle is the rotating magnet. Some other systems used many little "spikes," many little windings, but mine is only 4.

 

[sophiecentaur]

I have a strong suspicion that the guys who did the last job just got it wrong. If you have three coils in different places around inside the flywheel then they will be producing volts in different phases. Adding them in series as you have done will not get the full voltage from them - they will tend to cancel each other out, in fact. The fact that there are more diodes in your block than just the one also implies that it must be a multiphase system. I am pretty convinced about this and I suggest you look at wikipedia and you'll see what I mean.
If you want the best out of the system then you will need to take outputs from each coil and put them each through a separate diode. You will need to take the other ends of each coil and connect them in common to the ground. This is, effectively, three half-wave rectified outputs from three different phases, which will give far more current and a smoother total waveform.
I don't think that a bridge rectifier would help particularly. You need to be a bit more savvy to get it working properly.

 

[yshtar]

Yes, maybe it was a multiphase system, I'm not sure. A two or three phase system, maybe.I know nothing about it.
About canceling each other, I think it was what happened with the first guy because he wound all three in the same direction, such as left, left, and left. The power flowed in the middle coil crashed the other two, and I'm sure it was why the coil was burned. But if the direction is left, right, and left, the power flows at the three coils in the same direction. It was how I did it, and it worked fine, but the power was too high so I finally separated one coil (the middle) to reduce the power. I can still put them together to get the full power, but it will only kill the bulb.

Btw, I have tested all today, and all worked well. I'm not exactly sure what went wrong, but I think you're right that it was not properly wired. It seemed there was a short somewhere. I relocated the tail light wire and used other source for it and the battery didn't lose power anymore. Thanks. I'd still be checking the rectifier if I didn't meet you.:)

 

[sophiecentaur]

Glad to have been of some help. This stuff ins't always obvious to the uninitiated.

I'd still think you would benefit from looking at some of the diagrams of charging systems for motorbikes. You will see many examples of several coils with individual rectifiers. You are clearly getting very adept at removing and replacing the flywheel and coil assembly, by now! I seem to remember mine had a Wodruff key which used to graunch the slot in the flywheel assembly each time I removed it. I was a bit ham-fisted in those days!

 

[yshtar]

I think everyone had bad moments the first time. The first time I used the common sealer, but it was not heat resistant. It melted when the machine was hot. I had to clean the inside. lol. I replaced the wire and used epoxy adhesives and it lasts until now.:)