6volts high amp DC regulator..

[TKS]

6volts high amp DC regulator.. HELP NEEDED!

Hi all,

I'm in the need of a high amp 6volts regulator..

the common 1,5Amps arent up to the job because they burn out when my servo's are trying to move.'

I now have 3 jacked up parallel and over a time i now measure 8,5 volts output...when disconnecting each for each.. i see that 2 of them are perfect giveing 6volts but one gives 10volts..

- any one a idea wy it would blew that one???
- anyone a better solution??
- when measuring the fault one i get an diode voltage of 1,7 from the reg output to the GND pin.. the other give higher that 1,99 / NO READING

Tks

 

[Nigel Goodwin]

You can't simply parallel IC regulators, that's why one failed!.

 

[mcs51mc]

Why not using a LM723 and some 2N3055 transistors in parallel?

Industrial power supplies works on these components. 24V 8A is no problem at all.

Do some search with Yahoo on LM723 and 2N3055 will result in more schematics than you need.

Check this one 13.8V 10A Is that enough?

 

[TKS]

mhhh

well ok, the problem i have is i haven't much room.

Will search for the Voltage regulator Ic's.

Can any NPN be used???

And Nigel is it totally impossible to hookup the 78xx series parallel or what would i need??

Tks

 

[Nigel Goodwin]

Re: mhhh

well ok, the problem i have is i haven't much room.

Will search for the Voltage regulator Ic's.

Can any NPN be used???

And Nigel is it totally impossible to hookup the 78xx series parallel or what would i need??

The problem is they are not designed to be used in that way, so they don't have any external feedback connection. To current share between devices you can simply feed them via low value resistors, just as you would with transistors, BUT these are then outside the feedback loop, so the regulation won't account for the voltage drop across them.

As you're feeding multiple servo motors, why not just feed them from seperate regulators? - this would share the load out - no need to stick to a single 5V rail!.

 

[TKS]

mhh

ok,

think i will try then first each servo on one regulator.

I will try an servo to measure it amps...

the higher the voltage the lower the amps sow maybe at 6volts..
(wich is maximum) i only need 1 amp...

we shall see what happens..

I'm measureing..

Tks

 

[Nigel Goodwin]

How many servos do you have anyway? - and they don't really need a regulated supply, they are usually fed from the 4.8V or 6V radio supplies.

 

[TKS]

Hi Nigel

I have 3 servo's
wich are pic controlled

1=throttle
2=clutch
3=Gear

Clutch and Gear ar Jumbo editions all are digital sow more torque and better communication.

they are also more precise..

(the reason was toruqe/precise)

the have an max fed of 6volts....

the project is mounted in a car sow the battery i have is > 10 volts to 14volts while charging...

Regards,

Tks

 

[TKS]

well

Measured the amps.....

To measure the amps i putted my meter in series with the device...

When the device was moving my meter could measure something because it takes very short time.

When i gave some force on the lever to move it from his position it the amps reach a max of 1,7Amp if the voltage drops i dunno know.

When i gave an reasonable amount of force you reach maximum 0,8amps..

when i want to win from the device it let me win but it then consumes 1,7amps and just waits for me to stop with the force...

conclusion: Looks like one Reg per Servo is defendable (its reasonable to choose the solution) because the force the servo has to cope with is many times less then what i give with the hand.. (in real life the servo always wins..)..

in case the machine fails or something fails and the servo would be defending his position and consuming 1,7amps.. it will simply put the regulator in Short Circuit mode i guess..???

When short circuiting the regulator my meter gives 1,86 amps...

Sow the regulator is bigger then the servo.


Nigel i just solder one reg per servo.

Thanxs for the tip.

Regards,

Tks

 

[TKS]

looks like the amps are on the low side.. and the servo needs more guts to move..

would the LM138/LM338
(5-Amp Adjustable Regulators) be of any good??

instead of the big transistor solution??

Tks

 

[TKS]

Yesterday i measured up the voltage regulator (6volts)
each of them powers now one servo.

When moving the servo with the badest job, i could read with my multimeter voltages as low as 4 volts!! and 6,12 when not moveing.

Does this mean the regulator cant deliver the amps?

regards,

Tks

 

[TKS]

I have found a Usefull LM regulator (LM138) wich will give me 5amps.
the problem is it is adjustable sow it means it doesn´t sees ground??

Is it true that if the input voltage changes on the part, that the output is also changed????

Wich little chip could make it auto adjustable?

 

[Hero999]

It's a floating regulator, it doesn't need to see groung to regulate properly, the LM138 will be perfect for your application.

 

[Oznog]

OK you need to understand something though.
While the reg is rated for 5 amps of current, that doesn't say how much power it can handle. Power is limited by heatsinking, and even with ideal heatsinking then package limitations come into play. 5 amps out with Vin-Vout=14v-6v=8v means 40 watts! That's a LOT of power.

There are a couple of things you can do. One is the servos do not necessarily need to be voltage limited. If you PWM the driving transistors, it's very possible to drive the motors at "normal" speed off 14v. It would help if the PIC used a voltage divider and its ADC to determine the input voltage and adjust its PWM duty based on that.

The other thing is a switching (buck) regulator. These are more complicated, they require an inductor and often an external transistor, but they're extremely efficient and generate little heat even at high power levels.

 

[adaminc]

I'd suggest searching for "pass transistor" schematics, pass transistor logic is where you use a transistor to supplement the regulator in order to pass more current. I think its what mcs51mc was suggesting. Using the term pass transistor will make it easier to look up schematics in google.

 

[TKS]

Well the good news is that it needs 2,25 amps peak power...
for only a couple of seconds...

will try first then we see (my mum brought yeserday the components...)

Tks

 

[Paul Obrien]

Try a simpler switcher from National **broken link removed** or http://www.datasheetcatalog.com/datasheets_pdf/L/M/2/6/LM2678T-5.0.shtml for a 5Amp reg the inductors do cost $ but so do heatsinks and inductors take up less space. These available in adjustable output also so 6V won't be a problem. At 90% efficiency batteries would last longer 6V*5W= 30Watts at 90% 33.3Watts will be used, a long way from the 70Watts with the linear solution.