Toyota FJ Cruiser Forum banner
1 - 15 of 15 Posts

·
Premium Member
Joined
·
326 Posts

·
Registered
Joined
·
1,059 Posts
You could use a zener, but you'd be limited to situations where low amperage is required (like swicago said) unless you built it into a larger voltage regulation circuit. Anything more than a few hundred mA, I'd use the 7805.

FWIW, I'd use the 7805. Easy as heck, fast to get going, pretty reliable. The only downside is they're about 40% efficient, with the rest unrecoverable as heat loss. It's fine for 75% of 5V applications though (and likely fine for yours). No heatsink should be needed unless you're running it at the upper limit of current draw or input voltage.
 

·
Banned
Joined
·
1,538 Posts
Discussion Starter · #8 ·
whoa, not worried about ripple effects, blackholes, or load times...
thank you.

I'm just trying to eliminate an AC adapter to run a 5v dc unit.
 

·
Premium Member
Joined
·
3,399 Posts
whoa, not worried about ripple effects, blackholes, or load times...
thank you.

I'm just trying to eliminate an AC adapter to run a 5v dc unit.
By Ripple, I meant that the 5VDC will not be 100% 5VDC if the aft cap is not applied accordingly to the draw. You may only have 4.3VDC, which might cause your device not to operate as expected. Just trying to save you a headache as to why your volt meter might read 5VDC(no load) and then when you connect your device and it doesn't want to power on.
 

·
Banned
Joined
·
1,538 Posts
Discussion Starter · #10 ·
so no lil 47 farad dropping diode then eh...i thought there would be a simple in line diode with a lil silver strip one side to tell me which way the flow goes... =(
 

·
Registered
Joined
·
1,059 Posts
You could also look at using an LM317, which has a 1.5A guaranteed current output rating. The only thing is that it's slightly more involved... You'll need to pay attention to the datasheet and do some simple calculations to find the resistors which will set your output to the desired voltage.

Not too hard though and easy to find at Radio Shack locally.
 

·
Banned
Joined
·
1,538 Posts
Discussion Starter · #14 ·
You could also look at using an LM317, which has a 1.5A guaranteed current output rating. The only thing is that it's slightly more involved... You'll need to pay attention to the datasheet and do some simple calculations to find the resistors which will set your output to the desired voltage.

Not too hard though and easy to find at Radio Shack locally.
Radio shack these days help is not a word used there. No one there even has a clue as to what is in the drawers anymore..
i'll check it out and report back.. is there a guide to show which pins are what etc...
 

·
Registered
Joined
·
1,059 Posts
Radio shack these days help is not a word used there. No one there even has a clue as to what is in the drawers anymore..
i'll check it out and report back.. is there a guide to show which pins are what etc...
:lol: Yea, RS is kinda pathetic...

What you're after is the datasheet, here.

I'll save you the trouble though... Look what I just found! LM317 Calculator

Look on the first page of the datasheet. If you can follow that schematic, you can do this.

Use the LM317 calculator to find your resistor values for R1 or R2. Set "Calculation of" to whatever you'd like to find, either R1 or R2. I've typically used 240 ohms for R1 as suggested in the datasheet somewhere, but you could use most anything that you've got, as long as the other is set appropriately. Fill in the Vout voltage you'd like (I'm assuming 5V) and your R1 resistor value. Use the calculate button to show you what R2's value needs to be. It also shows you the re-arranged equation (from the datasheet) that is used to calculate these values. Play with it and use something close as far as standard resistor values go to achieve your target voltage as close as possible.
 
1 - 15 of 15 Posts
Top