First of all, as this is my first post in this forum, I would like to introduce myself and thank the rest of the participants for their contributions and help.
I am glad to take part in this community and hope to be able to help in return, in anyway I can.
Anyway, I have a rather old motorcycle which uses an excited field alternator.
For this type of alternators, voltage is dependent on the rpm and the current in the coil. As rpm in the alternator are dependant on engine speed, the only way to control the output voltage is through current control.
The regulator in this motorcycle, therefore, acts like a "current tap", which allows current to pass to a coil until a certain voltage is reached (around 13,5V-14V if working properly). If that voltage is reached, the regulator "closes" and allows no more current to pass.
Well, when restoring the bike, I decided to switch to a lithium battery, which the original regulator could not fully charge.
I made some research and came across an interesting website (http://gpzweb.s3-website-us-east-1.amazonaws.com/RegRec/GPZvRegExciteField.html), so I built the excited field voltage regulator using the following diagram:
(I can only acknowledge the merit of the person who created it and who unfortunately is no longer with us)
In summary, by varying the R4 resistor, the output voltage can be adjusted. (The whole circuit analysis can be checked in the original website)
It works properly but from time to time (excessively often should I say), it blows the indicators or the headlight bulbs. It also blew an USB charge socket that I fitted, including the capacitor.
Upon some inspection, everything seems to be in good conditions, all BJTs are OK, Zener, resistors, etc.
Instead of tunning the regulator with the engine running, I used a laboratory power supply to feed the regulator (with it connected to the motorcycle coil). I set 14,5 V in the PS and then tuned the potentiometer until the current in the coil started to drop (measuring it with an amperemeter).
Do you think this could this be the cause of error? Should I proceed in another way? It’s an old bike and it’s quite hard for me to set the bike at the desirable rpms, and I don´t want to cause unnecessary wear to it.
In addition, I have some questions about the circuit though, please forgive me if they are stupid, but my knowledge in electronics is limited.
1) First of all, what is the point of using 2 resistors in line with the Zener? Wouldn’t it act as a single resistor of a higher value? Keeping in mind that one is 100 ohm and the other 0,8-1k.
2) The other question I have is about the Q1 BJT. The base current is quite high, so a lot of power is dissipated and it gets rather hot. Could a MOSFET version be made in order to make it run cooler? Can someone enlighten me with this or make a little sketch? I'm completely lost here...
Thanks a lot
I am glad to take part in this community and hope to be able to help in return, in anyway I can.
Anyway, I have a rather old motorcycle which uses an excited field alternator.
For this type of alternators, voltage is dependent on the rpm and the current in the coil. As rpm in the alternator are dependant on engine speed, the only way to control the output voltage is through current control.
The regulator in this motorcycle, therefore, acts like a "current tap", which allows current to pass to a coil until a certain voltage is reached (around 13,5V-14V if working properly). If that voltage is reached, the regulator "closes" and allows no more current to pass.
Well, when restoring the bike, I decided to switch to a lithium battery, which the original regulator could not fully charge.
I made some research and came across an interesting website (http://gpzweb.s3-website-us-east-1.amazonaws.com/RegRec/GPZvRegExciteField.html), so I built the excited field voltage regulator using the following diagram:
(I can only acknowledge the merit of the person who created it and who unfortunately is no longer with us)
In summary, by varying the R4 resistor, the output voltage can be adjusted. (The whole circuit analysis can be checked in the original website)
It works properly but from time to time (excessively often should I say), it blows the indicators or the headlight bulbs. It also blew an USB charge socket that I fitted, including the capacitor.
Upon some inspection, everything seems to be in good conditions, all BJTs are OK, Zener, resistors, etc.
Instead of tunning the regulator with the engine running, I used a laboratory power supply to feed the regulator (with it connected to the motorcycle coil). I set 14,5 V in the PS and then tuned the potentiometer until the current in the coil started to drop (measuring it with an amperemeter).
Do you think this could this be the cause of error? Should I proceed in another way? It’s an old bike and it’s quite hard for me to set the bike at the desirable rpms, and I don´t want to cause unnecessary wear to it.
In addition, I have some questions about the circuit though, please forgive me if they are stupid, but my knowledge in electronics is limited.
1) First of all, what is the point of using 2 resistors in line with the Zener? Wouldn’t it act as a single resistor of a higher value? Keeping in mind that one is 100 ohm and the other 0,8-1k.
2) The other question I have is about the Q1 BJT. The base current is quite high, so a lot of power is dissipated and it gets rather hot. Could a MOSFET version be made in order to make it run cooler? Can someone enlighten me with this or make a little sketch? I'm completely lost here...
Thanks a lot