lab power supply

[not1xor1]

after looking at various ways to control a fan rather than just having it running found a little 555 timer fan control uses a npn transistor and thermistor so I’ve incorporated it into the scheme but before I build it in was wondering if any of you enlightened chaps might cast your eyes over the scheme so far oh i re drew the 555 to reflect it in reality rather than schematically its easyer to follow for me

I'm sorry, but that circuit (I'm referring to the overall one, not just the fan control) just doesn't make any sense. It looks like a random assemblage of electronic components.

[glinjik]

thankyou for you reply but could you explain your point? ie constructivly point out problems errors 

after looking at various ways to control a fan rather than just having it running found a little 555 timer fan control uses a npn transistor and thermistor so I’ve incorporated it into the scheme but before I build it in was wondering if any of you enlightened chaps might cast your eyes over the scheme so far oh i re drew the 555 to reflect it in reality rather than schematically its easyer to follow for me

I'm sorry, but that circuit (I'm referring to the overall one, not just the fan control) just doesn't make any sense. It looks like a random assemblage of electronic components.

the cicuit is a well know one its all ove the intenet im trying to adapt it to suit me i keep changing things and all is working so far all the parts are recovered for old stuff except bd140, 2n3055, and bd140 oh and the volt monitor, my next problem is restricting the voltage to fan contol i put in a zener 12v but its getting vey hot is the wattage to low? or is there a better way to achive 12v it needs to come from the rectifier so it wont disrupt any other part of the circuit and when the circuit is switched off the fan will keep running untill components are cool that is indicated by the led and the i can switch off the mains input

[MarkF]

after looking at various ways to control a fan rather than just having it running found a little 555 timer fan control uses a npn transistor and thermistor so I’ve incorporated it into the scheme but before I build it in was wondering if any of you enlightened chaps might cast your eyes over the scheme so far oh i re drew the 555 to reflect it in reality rather than schematically its easyer to follow for me

I'm sorry, but that circuit (I'm referring to the overall one, not just the fan control) just doesn't make any sense. It looks like a random assemblage of electronic components.

Right, the OP introduced some errors into the last few versions.
Here is what I think it should be IHO (with a few unnecessary components removed).

[george.b]

my next problem is restricting the voltage to fan contol i put in a zener 12v but its getting vey hot is the wattage to low?

Why don't you check your Zener diode's datasheet? Then you'll have your answer.

or is there a better way to achive 12v

Yes. Use a 7812, or use a transistor as a buffer for the Zener.

[glinjik]

Why don't you check your Zener diode's datasheet? Then you'll have your answer.

that indeed would be a great idea.....but im using recovered parts and there are no markings on the zener i obviously checked its voltage but thats all i can go on other than its physical size

i like the little circuit but i dont have the parts so what i think is il put in a lm715 circuit with a fixed voltage (i have lm315's

i did move the zener to just restrict the voltage to the fan but its still getting to hot like i can smell it

my problem is i live off the beaten track a bit and getting parts is a lot of trouble so i take apart junk to recover what i can but thank you for your answer all the various opinions are greatly apprieciated the fan control circuit works well no parts over heating apart from the zener the whole circuit can push 3 amps no problems just this little fan control that doing me in

[glinjik]

Well here is my latest incarnation fo your enjoyment i know its a bit odd adding a 317 just to regulate voltage to a fan circuit but it will work i only using what i have here so this is my solution now to build the last part circuit board is getting crowded bu here goes...

[glinjik]

update the lm317 works great but i think still too much current coming in i wonder if i can add a resister befor 317 to restrict the current i fan only needs 0.15A and bd140 is getting hot as well 317 both need heatsinks

[glinjik]

well looks like i found my own answer to this question due to not having the parts availabe or volt regu;ator i think the answer is a secondary transformer i have plenty of 12v trabsformers so im looking at tomorow to redraw scematic to include a secondery transformer with output straight to the fan control circuit 12v transformer only puts out 1a at most should solve the problem

[george.b]

that indeed would be a great idea.....but im using recovered parts and there are no markings on the zener i obviously checked its voltage but thats all i can go on other than its physical size

Fair enough. Well, the glass body Zeners you usually find on stuff will be 1W, tops. 500mW are also common.

[MarkF]

Well here is my latest incarnation fo your enjoyment i know its a bit odd adding a 317 just to regulate voltage to a fan circuit but it will work i only using what i have here so this is my solution now to build the last part circuit board is getting crowded bu here goes...

You have diode D6 in the wrong place.  No current will flow to the 2N3055 transistors where it is.

[glinjik]

thank you for your reply please explain why d6 prevents current flowing and if it is wht am i getting 3 amps (when i crank it up) on the emmiters of 2n3055? here is the original drawing well i doubt its original but its where i got it

[not1xor1]

after looking at various ways to control a fan rather than just having it running found a little 555 timer fan control uses a npn transistor and thermistor so I’ve incorporated it into the scheme but before I build it in was wondering if any of you enlightened chaps might cast your eyes over the scheme so far oh i re drew the 555 to reflect it in reality rather than schematically its easyer to follow for me

I'm sorry, but that circuit (I'm referring to the overall one, not just the fan control) just doesn't make any sense. It looks like a random assemblage of electronic components.

Right, the OP introduced some errors into the last few versions.
Here is what I think it should be IHO (with a few unnecessary components removed).

that circuit still doesn't make any sense. Both voltage regulation and current limit are really bad.
You can get similar results with just a potentiometer in parallel to a shunt regulator (e.g. TL431) plus a darlington to provide enough current for the power transistors.
And I' can't see any reason for not using just a BJT between the base and emitter of the power transistors.
Much better results might be achieved by several LM317 in parallel with ballast resistors (see the datasheet).

[not1xor1]

Well here is my latest incarnation fo your enjoyment i know its a bit odd adding a 317 just to regulate voltage to a fan circuit but it will work i only using what i have here so this is my solution now to build the last part circuit board is getting crowded bu here goes...

You have diode D6 in the wrong place.  No current will flow to the 2N3055 transistors where it is.

(Attachment Link)

BTW if the diode (in glinjik schematic) were correctly polarized it would not withstand currents greater than 1A (and would be useless).

[glinjik]

im thinking that diode is not serving any purpose at all i might remove it and check results but the volt control and currnt control work very smoothly with no problems even shorting the output across a 15w resistor getts good results although i only tried that for a few seconds to see what amperage i could achive the only problem is getting 12 volts to the fan circuit and keeping the current low without using a transistor other than a lm317 or a volt regulator at the moment the lm317 and bd140 are getting too hot thinking of putting in a secondary transformer to achive the 12v low current power 4 is the latest as of now

[MarkF]

thank you for your reply please explain why d6 prevents current flowing and if it is wht am i getting 3 amps (when i crank it up) on the emmiters of 2n3055? here is the original drawing well i doubt its original but its where i got it

I believe D6 is intended for over-voltage protection on the output (i.e. The device being powered has a voltage on its power rails that is higher than this circuit is set for).  It is only working for you because I suspect your wiring does not match the circuit diagram.


Your last circuit -- WRONG

How does the current go backward through the diode, D6, to the 2N3055?
NO collector current!




Your first circuit (Reply #7) -- RIGHT

[MarkF]

after looking at various ways to control a fan rather than just having it running found a little 555 timer fan control uses a npn transistor and thermistor so I’ve incorporated it into the scheme but before I build it in was wondering if any of you enlightened chaps might cast your eyes over the scheme so far oh i re drew the 555 to reflect it in reality rather than schematically its easyer to follow for me

I'm sorry, but that circuit (I'm referring to the overall one, not just the fan control) just doesn't make any sense. It looks like a random assemblage of electronic components.

Right, the OP introduced some errors into the last few versions.
Here is what I think it should be IHO (with a few unnecessary components removed).

that circuit still doesn't make any sense. Both voltage regulation and current limit are really bad.
You can get similar results with just a potentiometer in parallel to a shunt regulator (e.g. TL431) plus a darlington to provide enough current for the power transistors.
And I' can't see any reason for not using just a BJT between the base and emitter of the power transistors.
Much better results might be achieved by several LM317 in parallel with ballast resistors (see the datasheet).

I think this WHOLE design is poor.

I am working on a circuit where I was trying to limit the current by limiting the base current.
It worked.  But NOT very well.

New design:

[glinjik]

I believe D6 is intended for over-voltage protection on the output (i.e. The device being powered has a voltage on its power rails that is higher than this circuit is set for).  It is only working for you because I suspect your wiring does not match the circuit diagram

thank you yes you are correct my drawing is in error it is actually wired correctly, i have removed the whole fan control circuit and the volt limiting 317 im looking for a way to control the in a different way i think the best and simplest way is in the following diagram although i dont have a bd139 i do have a great big igbt so im going to try than instead report back at next version

[glinjik]

hi so my power pupply parts woes this morning got a knock at the door and a friend rought me this sack to see if i needed anything when i opened it woww its like early christmas maybe il find a fixed 12v volt regulator an awfull lot of transistors and big caps looks like computer power supplies or industrial power supplies, its nice to have friends of course im keeping the lot 

[glinjik]

after my windfall of components i finally finished the power supply its stable and functions well ive added heat sinks where i can tomorow i will put it in its case tomorow and do a few pics of the final product of course i will mod it at some point and add a amp meter im looking for a 0-5 a meter for now it will do hares the final scheme i know not perfect but im only a buiginer so thats my excuse merry christmas to you all in the wesern world here its not chrstmas till 6 jan but new year is the same

[george.b]

Something's missing from your MOSFET's drain, no?

[glinjik]

Something's missing from your MOSFET's drain, no?

well spotted an error an the ctr/c ctr/v ni miltisim, paint,save as  mery xmas

[glinjik]

happy new year to all

so carrying on with the development of my basic power supply the fan control i added is not as good as i hoped the transforer suffers when the fan kicks in and it is very difficuly to adjust tried different thermistors 2k 5k 10k 15k 47k got a whole bunch from my scrap power supplies so whilst i was hunting i had a look inside some old security cameras and found what i thought were 12v transformers turns out they are 19v with a volt regulator at 12v so i thought hm maybe i can rebuild is into a basic power supply and run the fan from that as A secondry transformer then i came across a fan control board the model is 3bs00383xxgp ver 1 so i installed a 15k thermister attached it to my rebuilt power supply and sems to work really well il do a schematic in tie bt for now some pics of just this part

[glinjik]

although this seems ok fan runs very quiet i think i would like it to turn off compleatley so im thinking remove the resistor highlighted in pic and put in a trimmer pot any thougts?

[glinjik]

this is what the fan power supply is ased on except i used bridge rectifier instead of 1n4007 1000uf cap is a820uf 200v lm7812 is a kp142ен8б that seems to be a russian equivalent of lm317? and the 1uf cap i stck in a 100uf 100v the small heatsink is enough to keep the volt reg cool it puts out a steady 11.81v the fan is 0.12A

[alex-sh]

So while it might have always been envisioned in your mind as the uSupply, anyone watching the PSU series from the beginning (as I did) would see it as morphing from a more traditional PSU design into the uSupply. And for sure, for someone looking for how the “lab PSU” series continues, it’s not self-evident from the video titles that the uSupply is the continuation. Looking for “PSU part 14” comes up dry.

These prototypes must be a figment of my imagination.
From left to right, dated 7/8/09, 3/5/10, 31/8/10
I showed that first prototype to Leo Simpson at Silicon Chip when he visited Altium in 2009 and dropped by my cubicle to say hi. Almost got it published in SC, but I just kept fiddling with it.

(Attachment Link)

So what happened? These never went to production