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cohippy

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I am attempting to build this field regulator ( all info about it is attached THANKS homepower.com)

My question is it says its adjustable.......HOW tho? I see no variable anything......I need a charge voltage of about 14.5 vdc from the alternator. Im using a 150 amp 22si version for its low rotor rpm vs output current.

any help would be so appriciated
 

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The variable resistor connected to pin 4 of the LM723 will vary the regulated voltage from about 12.5 V to about 16.7 V

Any specs on what i should choose? Ω & wattage?

Also a friend looked over the schematics and is looking for the same setup for himself. and said I should use 100v capacitors not 25v opinions?

Many thanks!
 
The circuit gives you the ratings and values :)

that trimpot is 1k Ohm
the 25V ratings for the electrolytic caps is ok its well above the operating voltage of the circuit
the 1/4 W (0.35W) wattage rating of the resistors as stated is also ok the only variation given is the 100 Ohm 10W resistor between the base of Q2 and collector of Q1 :)

cheers
Dave
 
ok Ive got everything ready to order from newark.com for this project and have been doing some investigating on this circuit, I think i understand how it works, my only question for someone out there is this:

is the current controlled by way of the NE555 timer a means of PWM (Pulse Width Modulation) if not how is this circuit controlling the current as the artical states?

Thanks
 
It is a horribly complicated PWM regulator which chops the field current on/off. What is this thing supposed to do that a $20 OEM replacement bought over the counter at PEP Boys wouldn't do????

Oh, I went and read the description. I see now that it is supposed to limit the initial charging current in addition to regulating the charging voltage later in the charging cycle. It is a dumb circuit, in as much it doesn't actually measure the current flowing into the battery; it just does an open-loop reduction of the available charging current.

If you are using flooded-cell batteries, the current limiting is unnecessary, they will take anything an automotive alternator can put out; with AGMs, current limiting might be beneficial, depends on your batteries, and how much current the alternator can put out.
 
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It is a horribly complicated PWM regulator which chops the field current on/off. What is this thing supposed to do that a $20 OEM replacement bought over the counter at PEP Boys wouldn't do????

Oh, I went and read the description. I see now that it is supposed to limit the initial charging current in addition to regulating the charging voltage later in the charging cycle. It is a dumb circuit, in as much it doesn't actually measure the current flowing into the battery; it just does an open-loop reduction of the available charging current.

If you are using flooded-cell batteries, the current limiting is unnecessary, they will take anything an automotive alternator can put out; with AGMs, current limiting might be beneficial, depends on your batteries, and how much current the alternator can put out.

This is for a 12 volt charger/generator for my RV to charge the 440Ah battery bank and to power the inverter. Im using a 160 amp 22si alternator. So what would you do differently besides buying a upwards to a $450 controller? Can you better design this? The changes Ive made are on Q2 and D2 as the 22si alternator rotor consumes about 9 amps so I'm going with a MJE2955TG on Q2 and a 10ETF06PBF on D2 to handle the 22si's power hungry rotor.

Remember there will be times (most of the time actually that I'm running the charger/generator at the same time im using the inverter, so I dont think having automatic voltage regulation is going to work well for the charging issue, as the battery bank is acting as a buffer, thus it would be reading incorrect voltages correct?

Also Im using 4 flooded deep-cycle batteries 220Ah each at 6vdc to create a 440Ah battery bank (Think equivalent to the Trojan T-105's is what im using)
 
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AFIK, the Trojans will take all of the available current from the alternator without even noticing. Look up the data sheet for the battery to see what the makers says. I 'm guessing that you are going to series-parallel the batteries, so the current from the alternator will divide between the two branches, reducing the peak charging current.

If I was looking for a Voltage Regulator for a 150A alternator, I would be looking at auto junk yards that might happen to have a police car, emergency vehicle, utility truck, etc. Leece-Neville makes such heavy-duty charging systems...
 
Could be you are using a small motor to drive the alternator. That would make the current control handy perhaps. I think I would use a darlington as the big transistor (maybe something like 2N6387) because you can't get enough base drive to propery run the standard transistor. Use a BIG heatsink.

My bad. You need a PNP. Try a 2N6667 or such.
 
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...
Remember there will be times (most of the time actually that I'm running the charger/generator at the same time im using the inverter, so I dont think having automatic voltage regulation is going to work well for the charging issue, as the battery bank is acting as a buffer, thus it would be reading incorrect voltages correct?
...

Not correct. It will work just like your car. Suppose that your total load is 50A. The batteries are partially discharged. The voltage is sitting at ~12.5V. You start the alternator, the VR is trying to get the battery terminal voltage up to ~14.2V, causing the alternator to go to full output of 120A. 50A goes to the load, the remaining 70A is available to charge the batteries. As the battery voltage rises to the VR set-point of 14.25V, the alternator output current tapers back. If you waited long enough, the battery charge current decreases to nearly zero, while the load is still sucking 50A, so the alternator will output just a bit over 50A.
 
Could be you are using a small motor to drive the alternator. That would make the current control handy perhaps. I think I would use a darlington as the big transistor (maybe something like 2N6387) because you can't get enough base drive to propery run the standard transistor. Use a BIG heatsink.

My bad. You need a PNP. Try a 2N6667 or such.

no ronv its a gas engine driven system.....not an electric motor......why would someone use electricity to make electricity? Im living off grid and dont have th $$$$$$$$ for PV panals

im powering the system with a 6hp Subaru EX17 that has a fuel consumption of 170 grams of fuel per HP per hour.....Also this is to limit the HP needed to drive the alternator to 2200 RPM this is all about effiency see attached pic of power curve....

I attached the power curves for the 10si 12si and the 22si power plans.....im using the 22si and I hope you can see why. and its NOT about the power produced as I was using a 10si and found just how inefficient it was......not to mention burning out rectifier diodes 2x's a month
 

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Could be you are using a small motor to drive the alternator. That would make the current control handy perhaps. I think I would use a darlington as the big transistor (maybe something like 2N6387) because you can't get enough base drive to propery run the standard transistor. Use a BIG heatsink.

My bad. You need a PNP. Try a 2N6667 or such.

ill be using the MJE2955TG why do you suggest the 2N6387?

and this heatsink https://www.newark.com/jsp/search/productdetail.jsp?sku=01M6666
 
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