Author Topic: 12volt FM or AM transmitter + Stepping 12v down to ~5v? (Read 3834 times)

HDL_CinC_Dragon · « **on:** December 06, 2007, 07:47:57 PM »

I tried googling on how to make a 12 volt FM transmitter but all I got were websites selling pre-made ones for as low as like 30 bucks or something like that. Does anyone know of a deent tutorial or at least a circuit diagram of how to make a simple xmitter?

I recently saw this one linked on the forums:
Link
But it uses at most 3 volts. If I used a resistor or a vreg to drop 12v down to ~2v, the heat would be ridiculous right? Not to mention horribly inefficient?

ed1380 · « **Reply #1 on:** December 06, 2007, 08:12:13 PM »

switching regulator

you can get them as free samples

HDL_CinC_Dragon · « **Reply #2 on:** December 06, 2007, 08:23:02 PM »

are they better than standard vregs/resistors? how efficient are they?
would this be a good option to use for that circuit to step 12v down to "2.6v"?

JonHylands · « **Reply #3 on:** December 06, 2007, 09:30:32 PM »

This is what I would use:

http://www.dimensionengineering.com/DE-SWADJ.htm

- Jon

HDL_CinC_Dragon · « **Reply #4 on:** January 12, 2008, 12:20:55 PM »

Thanks for the reference on that Jon. I would be very active in trying to get a hold of one of those if it wasnt so expensive >_< I doubt these things can be obtained as samples since theyre so expensive huh? And im also assuming that just using some resistors in series to step down the voltage would be a bad idea right? Since they dont regulate anything, if I was getting 18volts as input and expecting only 12, I would fry my circuit... damn I hate money restrictions lol

ed1380 · « **Reply #5 on:** January 12, 2008, 01:49:42 PM »

that thing is expensive since it's a pc board with all the plugs and stuff

looks around here
http://para.maxim-ic.com/cache/en/results/4632.html

paulstreats · « **Reply #6 on:** January 12, 2008, 02:57:52 PM »

if youre not stepping down too much you can use resistors or pots.

e.g.

i have a camera module that operates on 3 volts, but only have a 3.3v regulator. So i use the regulator as normal to provide 3.3v and then from that have a pot connected to a resistor connected to gnd. If i add a connection between the pot and the resistor i get a new voltage level depending on how i set the pot
note: this is okay for small shifts or steps down, but i wouldnt recommend it for a massive step

HDL_CinC_Dragon · « **Reply #7 on:** January 13, 2008, 11:22:55 PM »

12v to 5v is a relatively large shift is it not? I mean 7 wasted volts is pretty significant... plus I would like to use some kind of regulator like the switching ones so that im getting a constant ~5v instead of my output voltage slowly going down with my source voltage from the battery... would it be difficult/expensive to just make my own little switching regulator? Size wouldnt really be a factor of concern for me.

paulstreats · « **Reply #8 on:** January 14, 2008, 01:19:39 AM »

Have a search for a 'buck' circuit, there are two types, one that increases voltage and one that decreases it. (these are essentially what a switching regulator is)

They usually comprise of either capacitors(up to 98 percent efficient) or inductor(~83percent efficient) plus a couple of transistors or mosfets.

Its more likely to cost about the same as just buying one unless you already have the components going spare

ed1380 · « **Reply #9 on:** January 14, 2008, 08:37:22 AM »

or getting a free sample

HDL_CinC_Dragon · « **Reply #10 on:** January 14, 2008, 09:02:57 PM »

@paul
I googled "buck step down circuit" but all I could find were circuits with inductors in them and I would very much like to go with maximum efficiency.

@ed
Any idea from where I can get one as a sample?

SmAsH · « **Reply #11 on:** January 14, 2008, 09:16:24 PM »

yea theres tones of sites that are willing to give you a free sample i've gotten heaps of them by advertising their names on my robots at comps...

ed1380 · « **Reply #12 on:** January 14, 2008, 09:23:26 PM »

i postd it in a thread named "12volt FM or AM transmitter + Stepping 12v down to ~5v?"

here it is
http://www.societyofrobots.com/robotforum/index.php?topic=2554.msg20004#msg20004

HDL_CinC_Dragon · « **Reply #13 on:** January 14, 2008, 09:40:42 PM »

Yeah I went to that link and stayed at it for quite a while too. I didnt see a sample button... until now >_< sorry ed!

Any model number in particular that you would suggest or should I search around some more on there? I narrowed my search down to 10 different models: Link

My only qualms about those devices is that theyre all SMD devices. I need ones that have the pins like this one.

ed1380 · « **Reply #14 on:** January 15, 2008, 05:35:07 PM »

under packaging it'll tell if it's smd of through hole etc

the sot and sop ones are smd w/ legs. you might be able to bend them out.

I'll look at teh part # of teh regulators i have since they're DIP and see if they're still available

ed1380 · « **Reply #15 on:** January 15, 2008, 05:41:12 PM »

look around here
http://www.allegromicro.com/en/Products/Categories/Sanken/index.asp

i have the 8050jd. the 8050jf is what you might want

dunk · « **Reply #16 on:** January 15, 2008, 08:14:47 PM »

i've used the LM2596 switching regulator quite a lot.
it's available in SMT or through hole versions. rated up to 3A.

if you plan on drawing a constant 3A from it i recommend using the through hole version because even though it's a switching regulator it still generates a bit of heat. at those sorts of loads you have to bolt it so something metal.

you need a few other components to make it work. all detailed in the datasheet.
probably the toughest thing about it is finding a shotkey diode capable of handling the return current but i've successfully used several 1A shotkeys in parallel in the past.

you can see it in use on the schematic here: http://www.societyofrobots.com/member_tutorials/node/25

dunk.

HDL_CinC_Dragon · « **Reply #17 on:** January 15, 2008, 08:43:24 PM »

cool, thanks ed

I just requested a sample of the JF. I owe you

hopefully theyll get approved

HDL_CinC_Dragon · « **Reply #18 on:** January 20, 2008, 12:18:29 AM »

I just got my Switching Regulators (I asked for 2 and got both of them

)
They dont fit in my breadboard though >_< so im either going to risk bending them to make them fit or im going to make a socket translator

ed1380 · « **Reply #19 on:** January 20, 2008, 10:01:15 AM »

what about getting some single strand wire. solder like 1" to each pin and then bend that as necesary for it to fit

HDL_CinC_Dragon · « **Reply #20 on:** January 20, 2008, 11:06:53 AM »

... darn it ed, stop being so friggen brain using! You make my brain feel sad!

Thanks for the tip ed, im gunna do that

ed1380 · « **Reply #21 on:** January 20, 2008, 01:44:26 PM »

brain using? lol.

it's my ghetto self

Steel_monkey · « **Reply #22 on:** January 20, 2008, 04:38:43 PM »

It looks like many questions are asked for many times again and again. What about creating "suspended" topic about voltage transformation with few important posts? I have this wonderful link: http://www.nomad.ee/micros/mc34063a/ ( as I know, L max should also be calculated, so it must be taken in account). Also linear regs require some info to be mentioned.

News:

Author Topic: 12volt FM or AM transmitter + Stepping 12v down to ~5v? (Read 3834 times)

Related Topics