You need to use M3 bolt and nut to tighten TO220 on the heatsink.And you need to buy thermal compound at computer store they are cheap.

 

and my local hardware store won't go "huh!?" when I ask for M3 bolt and nut... probably a stupid question

 

The quantity of heat to be dissipated equals voltage times current.

For 1.5 amps times (12 - 5) volts that is about 10 watts.
It does not matter what method you use to drop the 12 volts down to 5 the power to be dissipated will be the same.

I have a dead Dell to finish sorting that I've been working on whilst conversing here and must now sign off till tomorrow.

You will need an MJE2955 for the negative half if you adopt both halves of my solution.

The 3055 (NPN transistor) will only do for the positive half.

 

Any hardware store should sell M3 nuts and bolts if they don't then they cant call themselves hardware store.

 

I think I'm going to do both. Object is learning, heatsinks as much as circuits. studiot I'm missing something here, is your solution already posted?

 

He posted the basic idea on page 3 he is waiting for your decision on what to build.
I'd recommend you to download LTspice and play with simulations a bit.

 

That simple, ok almost, no really didn't notice that, I'll build that easily, just the whole heat problem thats peeiing me off

 

I'll sign off for today then aswell, getting late. when you return studiot, I'm going with your solution, definitely.

 

I'll sign off for today then aswell, getting late. when you return studiot, I'm going with your solution, definitely.

MJ2955 - High Power PNP Silicon Transistor, T0220 (SEM62H)
R13.78
MJ2955 High Power PNP Silicon Transistor, complementary to the 2N3055.

Vce: 60V
Ic: 15A
P(W): 150
hfe: 45
Freq: 4MHz
TO220 Package.

Not the one you want?

this the one you want?

35M4061
Part Number MJE2955T
Description PS TO220 BCE 60V 10A MJE2955T
Manufacturer ST MICRO
Sold In Each
Minimum Order Qty 1.00
Alternate Part Number
Memo PNP SILICON BIPOLAR TRANSISTOR, TO220, 60V, 10A, 2MHz



AND this one I have 4 of:

MJE3055 - High Power NPN Silicon Transistor (SEM53H)
R9.78
MJE3055 High Power NPN Silicon Transistor

Vce: 60V
Ic: 10A
P(W): 75
hfe: 100
Freq:
TO220 Package.

 

Dont worry about heat too much.Heat problems can be fixed easily with a simple heatsink.


The ones you already have should be good to go.

 

last question then I'm really off: what wattage will the potentiometer need to carry, 'cause affordable ones max out at 0.75W

 

0.5W pot would work fine with voltage regulator.

 

last question then I'm really off: what wattage will the potentiometer need to carry, 'cause affordable ones max out at 0.75W

Just remember that power is voltage*current. If you size the pot properly, you shouldn't have any problem using a pot rated for 750 mW. Figure out those two things and you have your power. Don't forget to build in a cushion. When practical, never ask a component to exceed more than half of its rated power handling ability and be very leery of exceeding more than about 75%. That's just a real crude rule of thumb -- some components can be abused pretty heavily and others need to be treated with more kindness. With experience comes an ability to judge when you can be brutal and when you must be gentle.

 

OK studiot, how does your solution work, and verify my possible transistors plz, if I can use the MJ2955 it would be better (at the closer store Yebo Elecrtronics fort777.co.za), but If I have to, I can get the MJE2955 at mantech.co.za (It looks as though the MJ an MJE are almost identical.)

 

If by hand drill you mean electrically powered drill then you can.You will need 3mm HSS bit and WD40 or some sort of oil to lubricate the drilling spot.
That heatsink should work fine.

hand powered, thought that's what hand drill means

 

I guess that you could drill with that but its going to be very slow.

 

When you decide to buy the transistor or regulator I would recommend you to look for ones in TO220 package only.TO3 is really pain in the as* to mount since it requires 4 holes and special thermal pad so you don't short circuit the pins.
You can buy LM350 if you decide to go with regulator solution.

Stock Code 35M5830
Part Number LM350T
Description REG ADJ POS TO220 33V 3A
Manufacturer FAIRCHILD
Sold In Each
Minimum Order Qty 1.00
Alternate Part Number
Memo POSITIVE ADJUSTABLE LINEAR VOLTAGE REGULATOR 1.2V TO 33V 3A TO220


This the one?

 

Stock Code 35M5830
Part Number LM350T
Description REG ADJ POS TO220 33V 3A
Manufacturer FAIRCHILD
Sold In Each
Minimum Order Qty 1.00
Alternate Part Number
Memo POSITIVE ADJUSTABLE LINEAR VOLTAGE REGULATOR 1.2V TO 33V 3A TO220


This the one?

what would the 5V setting be on this regulator, or do I need to use a potentiometer?

 

Yes but you don't need regulator if you are going with studiots solution.You need two resistors to get fixed voltage output.Search for lm350 resistor calculator.

 

Yes but you don't need regulator if you are going with studiots solution.You need two resistors to get fixed voltage output.Search for lm350 resistor calculator.

I'm going with both solutions, education in both, and my projects are purely educational, it needs no real word application.