0-30V Stabilized Power Supply

[besarmatis]

Will you try the avr programming for vmeter and ameter?

 

[effenberg0x0]

Will you try the avr programming for vmeter and ameter?

Yes, definitely. I want my PS to have two outputs. and I got two LCDs here for the meters.

 

[besarmatis]

Think about auto cooling system using some of the thermal sensor with AVR. It very easy to do that using atmel microcontroller, thermal sensor and the L293 logic motor controller.

 

[effenberg0x0]

A good idea. My current heatsinks are so inadequate I'm considering leaving fans on non stop. Other options are Peltier modules, CPU coolers, etc...

 

[besarmatis]

Of course, leaving fans non stop has it's own pluses: less heat in the case, but it is the most simple way. For us - electronics it is not fun...
Sometimes I think, why factories can do better, why cannot I built even more better project, even it is not worth the price, but it is fun...

 

[effenberg0x0]

I think any decent Power Supply project built correctly will be better than commercial units. I'd say more than 90% of the commercial units I see in the market are cheap things that don't look like they will last 6 months. And, of course, it's always more entertaining to build it, no matter the price and time spent. That's why we're all here for anyway.

For example, one of the features I'd like to add to this project are digital controls instead of potentiometers ("+" and "-" push buttons). Don't know how yet. It's absolutely unnecessary, but it's cool.

 

[besarmatis]

I'd rather stay with the potentiometers, because I think it would get me annoyed to push buttons from 0V all way to 30V

But I think you want digital to analog converter.
Or maybe you can make something with the PWM signal.

 

[PicMaster]

I had a play with the older design at making digitally controlled, It worked very well I had a coarse and fine settings for the voltage, The coarse did 1V steps and the fine did it in MV steps, But stupid me put to much power out and blew something up on the PCB, I did not invetsigste any further has I want to build the latest version before I  start playing again, I keep reading this topic and the more you guys seem to all the have fun  ;D,  thhis makes get the urge to start playing agian but I has had to put it on the shelf due to other commitments, but now it's coming up to Christmas and christmas is the time to start playing. So I shall blow the cob webs of it and dig deep to find the code I used and get designing,  ;D
I shall design my own PCB to accpect both digital and pot's. That if the digital part does not work out i can stick pots in.

I can remember asking this in the old topic before we lost it but was based on the older version. What is the voltage coming out of U1 pin is was it about 11V or something like that ?

Another question how much of  the old documentation relates to the newer design IE. functions wise ?

 

[audioguru2]

The original circuit had many parts overloaded. The new version fixed the overloads by using parts with a higher power rating.
The original circuit did not meet its spec's. The new version does.
The new version fixes all the problems with the original version.

U1 has a 5.6V zener diode at its input and a voltage gain of 2. Then its output voltage is .....?

 

[effenberg0x0]

Pi (π) ?

 

[effenberg0x0]

Has any of you ever used these "PC OScilloscopes" that use the PC USB port? What about even cheaper units, that use the PC Mic In port? I'd like to hear some opinions on the quality of these things but can't find a user.

 

[karthikeid]

hi
from this circuit can i get a negative power supply or some other circuit is needed??

 

[audioguru2]

from this circuit can i get a negative power supply or some other circuit is needed??

Connect the + output to ground then the - output is a regulated variable negative supply.

 

[Timmymna]

Just finished reading this thread and I think I'm going to give it a try.

I have been looking on Farnell's site to find a suitable transformer but I'm a little confused at what specs I'm looking for.
In the latest specs it states a 28VAC 4.3A 118VA transformer, I can't see anywhere that says what the max and min should be.
A few posts back it mentions the voltage shouldn't be too high as to cause overheating and higher power losses but must also be able to provide the current required.

Your transformer is too small for a 5A power supply.
It is rated at 30V x 5A= 150VA. But the project makes 42.4V so when the output current is 5A then the transformer will be overloaded with 42.4V x 5A= 212VA.

From this comment could I use this transformer? It is 2x 30V, Secondary Winding:80VA, Secondary Current Rating:2.67A.
If I wired the two secondary's in parallel I get 30V with 160VA, giving 5.3A. If the project requires 42.4V then that still gives me 3.77A, (building the 3A version). Also taking into account peak voltage being < 44V for the opamps.

I'm not sure if this is correct or if I've taken some stuff out of context, I'm trying to understand how to select the best transformer for the job because there's also a 160VA, 2 X 25V transformer but is the 25V too low? Also it's nearly twice the price so trying to justify which is the better option.

Thanks and please feel free to point out my many mistakes 

 

[effenberg0x0]

As the voltage oscillates in the outlet, I can also see voltage changes in the Power Supply Output. Voltage in the outlet oscillates a lot more than I thought, about twice every minute +1 to +4V. Can't still calculate how much oscillation this creates in the PS output (single channel multimeter).

A first idea to fix this was to use a Voltage Regulator such as this: http://www.apc.com/products/category.cfm?id=12&subid=57

Or maybe you have any tip to make the PS output stable despite AC voltage changes in the outlet?

Thanks,
Effenberg

 

[audioguru2]

Just finished reading this thread and I think I'm going to give it a try.

I have been looking on Farnell's site to find a suitable transformer but I'm a little confused at what specs I'm looking for.
In the latest specs it states a 28VAC 4.3A 118VA transformer, I can't see anywhere that says what the max and min should be.
A few posts back it mentions the voltage shouldn't be too high as to cause overheating and higher power losses but must also be able to provide the current required.

... could I use this transformer? It is 2x 30V, Secondary Winding:80VA, Secondary Current Rating:2.67A.
If I wired the two secondary's in parallel I get 30V with 160VA, giving 5.3A. If the project requires 42.4V then that still gives me 3.77A, (building the 3A version). Also taking into account peak voltage being < 44V for the opamps.

Yes, the 160VA transforer is able to allow the output current of the project to be as high as 3.77A.

I'm not sure if this is correct or if I've taken some stuff out of context, I'm trying to understand how to select the best transformer for the job because there's also a 160VA, 2 X 25V transformer but is the 25V too low? Also it's nearly twice the price so trying to justify which is the better option.

Even the designers of this kit did not calculate the amount of voltage losses there are.
They said to use a 24V transformer but then the measured max output voltage at 3A was only about 25VDC.
In the latest version a 28VAC transformer will be fine. Your 30V one is also fine.

 

[PicMaster]

This is my schematic for the power supply, I've check it over but would like someone just to check it over and make sure I've not missed any  thing or any errors This will be a great help, If all correct I then shall transfer to the PCB layout tool,

I've gone for the option of C1 with R1 Across the cap mounted on the case wall and the same for the bridge rectifier, Q4,Q5,Q2,R23,R24,R16 also shall be mounted on a PCB bolted to the heatshink.

Once I know the schematic is 100% correct then I will know that the PCB will be 100%

EDIT: I've missed out D9 that is added
Thanks

Power_supply_V2.pdf

 

[audioguru2]

This is my schematic for the power supply

Why will ZD3 reduce the positive supply to U1 and U2 when the transformer is 30VAC? It might cause the max output voltage to be less than 30V when the current is max at 3A.

The 30V transformer might have an output of 31.5V without a load then its peak voltage is 44.5V and the rectifier bridge will make a positive unregulated supply of 43V which is less than the max allowed 44V for an MC34071 or TLE2141 opamp. 

 

[PicMaster]

Why will ZD3 reduce the positive supply to U1 and U2 when the transformer is 30VAC? It might cause the max output voltage to be less than 30V when the current is max at 3A.

I seen it in an earlier posting so I thoght I'd add it has you could just put wire link if not need but if it is needed and it's not here it make it look unitdy, But if it's not needed then I will take it out

I've already started to lay the PCB out for it

 

[audioguru2]

The performance of a low voltage (less than 5.6V) zener diode is poor. It conducts current when it has half its rated voltage and its voltage changes with temperature changes.