OK, I have a nice bag for the empeg/riocar now, and like many (most) of us Im totally addicted to having it around. Problems arise when I take a trip in someone else's car...

My thought was to add a small, 12v powered "local FM stereo" transmitter to the bag. Then I'd be down to just one connection (12v lighter plug) needed and it can go with me anywhere. I've found a few FM transmitters that fit the bill, but any that are 12v are either:

1) too large to fit in the bag comfortably or
2) Use one or two AA batteries. (1.5 or 3V)

I found this one, which is small, cheap ($20) and would probably work well enough.

http://www.dak.com/reviews/2005story.cfm

(Yeah, I know, this guy has sold electronic crap for years, he's baaaaack)

Anyway, question is - is there anywhere I can easily pull 3Vdc from the empeg itself? Or do I need to concoct a 3v power supply of some sort? (I seem to remember an IC that could do this with like no additional parts for about $5...)

Thoughts????

I had that one it didn't work for crap.

I got this one from radio shack and it works much better
Link

I have the same one from Radio Shack, but I agree that having one that runs off 12 v (or at least has an adapter to step down from 12 v.) would be preferred. Anyone know of one?

Hey cool! I didnt know RS carried that one. I had seen that online at... oh some MP3 site, but it was $50 plus shipping.

How long does it run on the AA battery? Hell, if it went at least 3-4 hours I'd be good with that probably.

How do these sound? Im assuming they sound about like the one I use in my dash now (I hate having my Empeg run through an fm mod, but its the easiest for now).

Gotta look through the IC catalog, Im sure there has got to be an IC regulator that will work for this...

-Jeff

See this post for a link to buy.com who has it cheaper with free shipping. I have it and it will definitely operate for over 4 hours on alkalines. It sounds pretty good, but probably less good than an FM modulator that sits in-line with your antenna. I was able to stand 25 feet away from the car, and the sound was still acceptable. I'm not sure what that test proves, but it works.

Thanks, I'll check that out.

Techie empeg guys, isn't a +5v line part of the serial port? I would think this thing would find 5v OK, since it runs on 3 normally.

Any thoughts on that? Am I mistaken?

[edit] nevermind, looked up the pinouts... My bad... Guess I'll just use batteries.

-Jeff

My rental car right now only has a tape player,
so by pure accident I stumbled over the irok 300w and ordered it yesterday.
Should be here tomorrow.
I'll give you some thought on it next week.

About the power supply:
You need 3 parts and solder them together to get to three volts - well, two parts if you use a zdiode - so where is the problem ?!

You need 3 parts and solder them together to get to three volts - well, two parts if you use a zdiode - so where is the problem ?!

No problem, except that he doesn't know which three parts or how to solder them together. You wouldn't want to share that information, would you?

LM317/LM117, 0.1uF cap between input and ground, 240 Ohm resistor between output and adjust, 330 Ohm (336 Ohm) from adjust to ground.

Depending on current draw (if below ~5 mA) you might need an extra ballast load for proper regulation. 600 Ohm from output to ground will draw 5mA...

Optional 1uF cap between output and ground.

Should fit in the battery compartment without any problems.

Spec sheet




There are probably much easier ways to get a 2.5 to 3.2 (about all regulation needed considering it's a battery powered thing...) voltage from the car, but the above is pretty general if someone needs other voltages and good regulation.

/Michael

Excellent, now that's just what I needed! I can solder stuff together, and have some real basic electronics knowledge and I just knew that there were IC regulators available. Thanks a bunch, off to the electronics store....

-Jeff

If you can't find a 117/317, you could probably get by with a fixed voltage regulator like the 7805 (can't seem to locate a 3V version (which would be 7803)) and 2 or 3 diodes in series on the output to drop about 2 of the 5 volt... The 78xx regulators just want caps on input and output, nothiing else.

Ten years, or so, I had a portable CD-player in my car. The entire content of the cig. adapter plug was a fuse and 7 1N4001 diodes in series...

/Michael

If you want to go completely over the top look here:

http://www.hobbytron.net/r-px1.html

mmmm...pirate radio....

-Zeke

Has anyone seen US distribution for the USB FM transmitter by Richfield Electronics Co.? It's an interesting product but I've never seen it for sale in the US.

http://www.globalsources.com/gsol/GeneralManager?&catalog_id=2000000003844&design=clean&language=en&action=GetSupplier&page=supplier/ProductDetail&supplier_id=6008808320280&product_id=8823346922&action=GetProduct

-Zeke

Hi Michael,

Would this work for something needing between 520 and 680 mAmps and about 3.0 - 3.6 volts?

Thanks,
-Ryan.

Yes, but you need to get the LM117/317 in a housing that can provide at least 1A.
Then you need to mount it on a decent heat sink - you'll be creating about 7.5W [(14-3)V*0.68A] of heat in the regulator...

What sort of consistency does the item need? A 7805 and 3 1N4001 diodes in series may be good enough. And IIRC the 7805 comes in heftier housings, at least for the higher current capacity models...

/Michael

I'm actually trying to step 5V down to 3.0 - 3.6V. It's for a DVI to proprietary lcd panel connector. I originally tried two diodes, but they don't seem to be doing the trick. Maybe I'm using the wrong kind. The panel's voltage needs to stay in that range and the current will change depending on what's displaying on the panel. The backlighting is powered completely separately.

Thanks a bunch,
-Ryan.

OK. It's good that you start with a lower voltage - less heat to dissipate. (About 1.4W [2x0.68])

Problem is that the 117 wants at least 3V difference between input and and output (meaning at least a 6V supply in your case, if you set a 3V output voltage)

Strange that the diodes didn't do the trick though - each should drop about 0.7 to 0.8V at those currents... (1N400x diodes or similar)

There are low drop regulators available, that should be able to work with < 2V difference, but I don't have any part numbers at hand...

/Michael

There are plenty of 3.3v LDO converters that will do it with one component, eg:

LM1117T-3.3 (farnell code 120-730, 800mA, TO-220 package, LDO)

Hugo

How about at low current; will the diodes still drop 0.7V? When a panel starts up, the DDC powersaving/display identification happens which wouldn't require much power at all. After this negotiation with the video card, the card will drive the panel with pixel information at full power.

Thanks,
-Ryan.

Should be around there, but you'd have to know how much/little current it draws in that mode to be sure...

The part Hugo mentioned above sounds like just what you're after...

/Michael

Thanks Hugo. This is a big help!

-Ryan.

Wow, I wanted to say thanks again. I got some sample LM1117T-3.3 parts from National yesterday and soldered one in place. The panel works perfectly!

You rock, Hugo.
-Ryan.