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Forum Index : Microcontroller and PC projects : hamfield 317 mod adjust bred bord

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sparkey

Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 819
Posted: 02:01pm 20 Aug 2011
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adjustable 1.2v to 14 volt 1.5 amps max...

::: this is what i have done please read this whole article befor doing this mod i dont

mean that you would nessarely want to do this but this is what i have done so do so at

your own risk ..ok... common sense ... ::please ...

::as i also am powering this with 15 volts and 2 amp supply ... if you draw a large amount of current from the 3.3 volt rail and or the 5 volt reg`s are getting extreemy too hot for your likeing .. you may be better off ..using the adjustable rail if your using .. 5 volts or even 9 volts and want a high current rail... well this should be adjustable between 1.2 volts to about 14 volts you may get a little more voltage depending on the config and how much current you supply ...

,also the pot is very touchy you should prolly go with a 2 k pot you would be much better off as the 10k pot is a bit like a log pot rather thana linear which u should be using and you should put a volt meter on the out put pins

" marked as +5v "

before connecting any thing up to it.... set the voltage correctly.. the circuit seems reasonably stable .. i have an anolog meter on its output ...you could use a simple code to display this voltage on the screen depending on your application...

::::as this is now your adjustable out put headder....

::method...

:i sugest a larger heat sink if you r going to be using the 317 to it`s full potential...

::i first removed the 7805 and the heat sink got some 1.2 mm enameled copper wire and a..2k 16mm pot and a 120 ohm 1/4 watt resistor and a 3.3k 1% 1/4 watt resistor.....

:change "r-4" to 3K3...

:get four lenths of enaml wire about 70 mm long 1.2 mm thick


: strip insulation with emory paper about 5mm on each end ....on the four pieces of wire...

:solder two lenths aprox70 mm long into the bottoms of the heatsink pins

: when looking at the front of the 317 writing side pin 1 is on the left pin 2 is mid

and pin 3 is on the right

:pin 1 adjust
:pin 2 output
:pin 3 is input

:attach the other two wires one to the input pin the other to adjust pin....

:from the output pin 3 to the adjust pin 2 solder a 120 ohm
resistor 1/4 watt 1% ...

:now at present i have mounted the 2k pot with its back glued to the board where the heat sink would be i just used some super glue to stick it there
and the pins faceing away from the board .....i put a knob from an old cb radio so its small....

: now solder a wire from the middle pin of the 2k pot... hook it up to the
the ground pin hole on the pcb ..that is pin two or middle .. hole...

:now take another wire ...hook itup to one of the outer pin on the pot and attach this to pin 1 on the 317 ...::

:: next mount the heat sink approx 70 mm high by attaching the two legs from the sink ,,facing it the same way it was facing before now attach the two support stand wires to the pc board

::: next attach one of the wires to pin 2 output pin and the other end solderd to pin 3 on the pcb which is the output...

:last wire is attached to pin 3 on the reg and then solderd to pin 1 on the pcb...

:thats it your done ......before using it first do a voltage check with a multimeter of you choice....set to volts...

:: footnote ::: you could get a piece of 1mm thick by 40mm by 18mm bend it at right angle drill two small mounting holes and some small bolts and drill a 6mm /7mm hole for the pot to fit the pot that way horizontaly. wiring stays the same....::: 2Nd foot note you could wire up a led on the input side of the reg at least you will know you have power going into the reg....Edited by sparkey 2011-08-23
technicians do it with least resistance
 
Bill.b

Senior Member

Joined: 25/06/2011
Location: Australia
Posts: 226
Posted: 12:58am 22 Aug 2011
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hi all

If you are connecting a load greater then 1 Amp, you will have to replace diode D1 as this is only ratted at 1 Amp

Also I am using a regulated 12v power supply therfore I have removed the 12 regulator
and bridged the in and out pins.

With D1 in circuit, this gives aprox 11.2 volts at the 12v terminal. if the full 12 volts is required then replace D1 with a bridge.

D1 is only used for reverse supply protection.

In the interests of the environment, this post has been constructed entirely from recycled electrons.
 
sparkey

Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 819
Posted: 01:37am 22 Aug 2011
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thanks bill with all that was in volved in putting up this post that s about the only thing i for got about

:change D 1 for a 1,5 amp diode actully if you omit it the circuit will still function its ony there for protection it is connected accross the regulator...regards sparkey... we are not in a perfect world but we try ...

:::actully there is no reason to change to a 1.5 amp diode it actully wiil work finejaust the way it is cause if a short does devolop it will short at a lower threashold....Edited by sparkey 2011-08-23
technicians do it with least resistance
 
sparkey

Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 819
Posted: 05:16am 22 Aug 2011
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well lets put it this way i havent had any trouble with the diode going short but i will short mine out and let you know what occurs will the diode protect the device i bet and usully diodes as a given go short much the same as any semiconductor if a present load of a reverse polarity was throwen accross it it would be a short there fore the current takes the path of least restance by passing the device while stil giving power to the rest of the cct....regards sparkey and if it does go open then the power sdupply would have to be in the range of at least ten amps ....
technicians do it with least resistance
 
sparkey

Senior Member

Joined: 15/06/2011
Location: Australia
Posts: 819
Posted: 09:45am 27 Aug 2011
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i just killed the 7812 on the b-board from mamfeild

the diode did not go short un fortunatley ....how ever i replaced it with a 78m09 1.5 amp 9 volt reg .......i had it on hand ......
technicians do it with least resistance
 
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