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Ok. Here it is. Still needs more review. I won't be able to fabricate for about 2 weeks.
http://www.mikeinkaty.com/6V_PowerSupply.pdf
http://www.mikeinkaty.com/6V_PowerSupply.pdf
Mike a few questions:
1.Are you going to build only a single board ?
2.Have you tested the circuit to work and satisfy your needs?
3.Are the LM350s mounted on the board?How will they be connected to the heat sink?
4.Didn't you say your transformer is a center-tap one?
If so, you can do a 2 diode full rectifier with center tape
(to eliminate 2 bulky diodes and simplify traces).
1.Are you going to build only a single board ?
2.Have you tested the circuit to work and satisfy your needs?
3.Are the LM350s mounted on the board?How will they be connected to the heat sink?
4.Didn't you say your transformer is a center-tap one?
If so, you can do a 2 diode full rectifier with center tape
(to eliminate 2 bulky diodes and simplify traces).
No, it does not have a center tap. The package said black and either yellow for 6v. Yellow and yellow for 12v. But not to connect any of the 3 wires to each other. I've never ran into that before. That's why I used a bridge.
Just making one for now. No, I have not tested it yet. Small aluminum fins supported by the VR plus a 2" muffin fan. Heat will be less with a lower delta-v. I've run the 350T encapsulated in heat shrink tubing and they would get blistering hot without shutting off. When I did the 3v delta and getting 1.6 A, the VR only got warm in a 1 hr test.
Might make a couple more in the future as constant current chargers.
I can buy this stuff cheaper than I can make them but where is the fun in that! I'm 74 years old and do this kind of stuff for the fun in it. My wife has been in an Alzheimers clinic for a year and I do better if I'm occupied with a brain teaser.
I have a degree in EE (Okla State 1965) but I've never worked with electronics as a profession. Always as a hobby. My career was in computer systems design and architecture.
I retired in 1999 and my assignment for my last 5 years was as chief intranet designer for the 5000 people in my department.
Mike
Just making one for now. No, I have not tested it yet. Small aluminum fins supported by the VR plus a 2" muffin fan. Heat will be less with a lower delta-v. I've run the 350T encapsulated in heat shrink tubing and they would get blistering hot without shutting off. When I did the 3v delta and getting 1.6 A, the VR only got warm in a 1 hr test.
Might make a couple more in the future as constant current chargers.
I can buy this stuff cheaper than I can make them but where is the fun in that! I'm 74 years old and do this kind of stuff for the fun in it. My wife has been in an Alzheimers clinic for a year and I do better if I'm occupied with a brain teaser.
I have a degree in EE (Okla State 1965) but I've never worked with electronics as a profession. Always as a hobby. My career was in computer systems design and architecture.
I retired in 1999 and my assignment for my last 5 years was as chief intranet designer for the 5000 people in my department.
Mike
Mike, just for future information, you don't need to connect any transformer wires together to make a full-wave rectifier with a centre-tapped transformer. Here's an example:-
Edit:
You need to make some circuit changes to do that. This isn't a constant-current circuit, only constant voltage.
The instructions on this pkg said not to use the black wire if using 12 volts. So, l just took what it said at face value and used the bridge. For a true center tapped trans. I connect the two ends of the windings together then between them and the 'center tap' you get half voltage at full current.
Someone above had asked me if it had a center tap (for testing at 6v). Maybe it does and the Chinese just didn't know how to say it!
Mike
Someone above had asked me if it had a center tap (for testing at 6v). Maybe it does and the Chinese just didn't know how to say it!
Mike
You can't do that. It's a dead short across the secondary, and will kill it.
It can be done with two separate windings, (4 wires), if you do it so that they're in phase, but not with a single, centre-tapped winding. (3 wires)
Mike,
I wish you both the best of health.
What you have is a center tape transformer!
"The package said black and either yellow for 6v. Yellow and yellow for 12v "
The center tape is the the black.
Very simple to verify that with an ohm test(and voltage test):
the resistance of yellow to yellow is 2X that of each yellow to black.
But,in this case,you can't use it in a 2 diode rectifier since it will only produce about 6*1.4=8.4 volts dc.
The12v with a bridge is the way to go.
In general,
keep in mind that you need some margin from the minimum of 3V delta to withstand changes like line variations,resistor tolerances etc.
Also,
note that you can control the "power dissipation balance" of the VRs with a trimmer in the "first" LM350 voltage adj.
Personally,
I would build that kind of project on a Veroboard or Perfboard .
Are you manufacturing the PCB yourself or "outsource" ?
I wish you both the best of health.
What you have is a center tape transformer!
"The package said black and either yellow for 6v. Yellow and yellow for 12v "
The center tape is the the black.
Very simple to verify that with an ohm test(and voltage test):
the resistance of yellow to yellow is 2X that of each yellow to black.
But,in this case,you can't use it in a 2 diode rectifier since it will only produce about 6*1.4=8.4 volts dc.
The12v with a bridge is the way to go.
In general,
keep in mind that you need some margin from the minimum of 3V delta to withstand changes like line variations,resistor tolerances etc.
Also,
note that you can control the "power dissipation balance" of the VRs with a trimmer in the "first" LM350 voltage adj.
Personally,
I would build that kind of project on a Veroboard or Perfboard .
Are you manufacturing the PCB yourself or "outsource" ?
Whatever.
I etch the board. If I screw up badly I etch another! I drill using a small drill press. I do need to get some tinning solution. That looks much better than tinning with solder. I use press & peel iron on sheets to get the traces to the CB. Then etch with ferric chloride solution. I buy the powder at a local Chem store.
It's been like 35 years since I've done much with electronics. I have forgotten so much and so much has changed. Luckily my eyes are still good and hands are still steady!
Mike
I etch the board. If I screw up badly I etch another! I drill using a small drill press. I do need to get some tinning solution. That looks much better than tinning with solder. I use press & peel iron on sheets to get the traces to the CB. Then etch with ferric chloride solution. I buy the powder at a local Chem store.
It's been like 35 years since I've done much with electronics. I have forgotten so much and so much has changed. Luckily my eyes are still good and hands are still steady!
Mike
Dorke, when used with solar panels I have observed the 350 still supplying current to 6v batteries with a delta as low as 2 v.
Mike, the dropout voltage, (not usually referred to as 'delta'), is about 2.4V at 2A and 25°C. Allowing for troughs in the input voltage when it's fed by a rectified AC source, about 3V is a good safe minimum to stick to. The dropout voltage is about 2V at 25°C when the current is a little below 1A. All of these values need to be 'de-rated' for higher temperatures.
Here's a link to the datasheet. It contains all of this info:-
https://www.fairchildsemi.com/datasheets/LM/LM350.pdf
Mike,
We need to keep in mind that the LM350 is a Voltage Regulator.
Hence it is specified like a VR :
Load and Line regulations being the most important characteristics and
ref. voltage accuracy and adj. current change the 2nd in importance.
Look at the datasheet from Ti,
they spec only for Vin-Vout= "dropout voltage" greater than 3V.
and for load regulation above 5V!
If we want a solid design(worse case design),
we should comply with the manufacture's specs.
The device may still work if we don't ,but the results are not to spec anymore.
So,like you said:
"I have observed the 350 still supplying current
to 6v batteries with a delta as low as 2 v"
Was your design a voltage regulator?what was the regulated voltage and it's stability?
Or was it a current source?what was the regulated current and it's stability?
In any case the out of spec working conditions had an effect on
charging current,charging time,and maybe battery life time etc.
I guess you studied vacuum-tubes as well...
Yes we forget a lot(and it is frustrating ,me too).
Nowadays in EE field ,2 years are a generation ,10 years an era...
We need to keep in mind that the LM350 is a Voltage Regulator.
Hence it is specified like a VR :
Load and Line regulations being the most important characteristics and
ref. voltage accuracy and adj. current change the 2nd in importance.
Look at the datasheet from Ti,
they spec only for Vin-Vout= "dropout voltage" greater than 3V.
and for load regulation above 5V!
If we want a solid design(worse case design),
we should comply with the manufacture's specs.
The device may still work if we don't ,but the results are not to spec anymore.
So,like you said:
"I have observed the 350 still supplying current
to 6v batteries with a delta as low as 2 v"
Was your design a voltage regulator?what was the regulated voltage and it's stability?
Or was it a current source?what was the regulated current and it's stability?
In any case the out of spec working conditions had an effect on
charging current,charging time,and maybe battery life time etc.
I guess you studied vacuum-tubes as well...
Yes we forget a lot(and it is frustrating ,me too).
Nowadays in EE field ,2 years are a generation ,10 years an era...
Last edited by a moderator:
You're not wrong there. I was out of the field for 10 years, and the combination of what I've forgotten and the advances in the intervening period has left me floundering a bit. Getting there though.Yes we forget a lot(and it is frustrating ,me too).
Nowadays in EE field ,2 years are a generation ,10 years an era...
These forums have helped enormously in that regard, especially forcing myself to think by helping solve other people's problems.
Not thinking anout electronics today. Mowing hay.
Using two LM350's won't work. Each regulator will drop about 3 volts.
Don't need to...its on the datasheet. Fig 6 "Dropout voltage".
Its closer to 2V but should leave some headroom...
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