Hi guys, recently i've been designing a vehicle remote ignition system.
For power for the arduino i was thinking of this:
Also, is this design any good?
Regards, Matt.
What is the load? The linear regulator alone says if your drawing more than 100ma its not worth it
check ebay out for some 12/24v to 5v 3A buck converter, I think I got one 4$, there ery small, much more effecient
I've bought two before and my multimeter said 5v and5.01v so id say there pretty good
I'm using this for my project. It is a DC to DC converter that won't loose half of the power to heat. You can hook a transistor to the circuit to get up to about 4 amps out of it. It is auto rated, and therefore has noise suppression and everything necessary to give you a clean signal.
One potential benefit of the ebay one is its not pccb mounted which can save you space, assuming you have space to put a small converter in, which in automotive there is usually space
I've tested the ones I have with my oscope and about 1.5amps load and its clean, I can't even see any ripple
its a nice little black box that you don't have to worry about
http://item.mobileweb.ebay.com/viewitem?itemId=270959601119&index=5&nav=SEARCH&nid=08497076835
here's an example <4$
Well the main reason for wanting to use the circuit above is to be able to design my own pcb and have it printed. but that doesn't matter 
Thanks guys for the link, that's awesome! i think i'll give the ebay one a try first.
Regards.
What is it going to be powering?
I made a mega shield for use in a car, and the first version used a linear regulator but with 800ma draw it couldn't handle it
Then I thought about one of those drop in replacements that are switchin but the cost was too much
the final version just has some terminals for 5v input , which saved alot of space and reduced heat
It's going to be for a remote vehicle ignition, so it'l only be powering two TIP122 transistors, and a sparkfun gsm shield which hits around ~2A at max bursts.
Also, quick question.
I have an input for the arduino to sense when the car is running, this is a 12V input.
Which would be the best way for the arduino to sense this 12V, ie, if 12V is applied, pin 4 goes high.
I would think a transistor, but not sure how exactly to wire it, nor what transistor to use.
Regards, Matt.
Keeping in mind that this would probably be just as susceptible to voltage spikes and such.
A voltage divider would work, just make sure that the max voltage will be no more than 5v even if the input is 15 volts, so it'll probably be less than 5v at most times, so long as its above 3.3v
Yeh, that's what i used in my original design, but i need strong protection against spikes and the like.
I decided to use a 12v coil SSR on a pull up resistor. so when the relay is engaged it sends 5v to input pin 4
Designed my first board with eagle, and sent off the design to my local pcb place :)|
Cheers guys
Sounds good, you could also use a 5.1v zener on the voltage divider output, maybe a small cap for spikes and even a 1k resitor before the input
Perhaps a little cheaper
Or an optocouler
Hmm.
I would've like to do that, as i'm having alot of fun learning eagle, but i've already sent off the board design to be made.
And i guess, i have a hard time finding which diodes, caps and regulators to use as i'm quite the noob.
i.e, when i find a design for power supply, i try and find all the components, and one online store will have one, but not the other and vice/versa.
Thanks for the help winner
regards.
Np, and remember there can be version 2 lol
I think I had about 6 revisions at 20$ a pcb until I was satisfied with my car module
