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12v Step-down?

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CCinPA

New Member
In looking around a bit... I believe "step-down" is the correct term.

12v automotive application. I need an adjustable "???" to step-down between 12v and 9(ish)v. Help?
 

dr pepper

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Welcome.
You can get cheap adjustable switching voltage regulators from ebay.
You do need to know the current rating of the device though, usually stated in mA.
 

dknguyen

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If your current is below 1A, you will probably use what is a type of step-down regulator called a "Linear regulator". You may also find them referred to as an LDO (low-dropout regulator).
 

CCinPA

New Member
Application: LED clock

Update: Need a solution with lead-wires. Heat-sink? Noise would be a problem for the automotive project.
 

dknguyen

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Application: LED clock

Update: Need a solution with lead-wires. Heat-sink? Noise would be a problem for the automotive project.
You won't need a heatsink if the current is low enough and the input and output voltage are close enough. But you might as well stick a $1 heatsink on it.

You'll have to mount the thing somehow. and solder on leadwires. Probably a small generic proto-board. You'll need one anyways since the regulator requires two resistors (to adjust the voltage) and two capacitors (one on the input and one on the output).
 

Pommie

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Just search ebay for a LM2596 adjustable module and set it for 9V or 10V. It should cost no more than US$1 incl postage.

Mike.
 

MikeMl

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Just search ebay for a LM2596 adjustable module and set it for 9V or 10V. It should cost no more than US$1 incl postage.

Mike.
... and give up ever using the AM radio in the car again...

My solution would be an adjustable LM317 type linear regulator...

If this thing draws any significant current, more than ~10mA, I sure as hell wouldn't be leaving it connected to the car's battery when engine not running... If it draws only a few mA, then no heatsink is required.
 

MikeMl

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dr pepper

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Yup I listen to radio4 on am in my vehicle.
The injectors in my car run off 48vdc, and that comes from 4 LM25xx's, very little noise on am even between stations, its all down to the job being done right.
 
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MikeMl

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...its all down to the job being done right.
Let me guess, put the LM25XX pcb in a shielded enclosure, with ferrite common-mode filters on both the input wires and output wires including filter capacitors? That is about the minimum that it takes to quiet those things down... Been there, had to do that.
 

Pommie

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I have a dual lighter socket to usb converter and if I charge my phone with it I can't listen to am radio in weak signal areas.

Mike.
 

dr pepper

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Mike at first I thought the enclosure was just plastic, after seeing inside a injector control module yes its metalized for screening, and there was what looked like some Emi filtering stuff, vehicle manufacturers probably have to conform to a load of rules.
 

MikeMl

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Mike at first I thought the enclosure was just plastic, after seeing inside a injector control module yes its metalized for screening, and there was what looked like some Emi filtering stuff, vehicle manufacturers probably have to conform to a load of rules.
Electronics installed in automobiles at the factory is tested for RFI and must meet rigid standards. I'm off to breakfast with the guy that used to do the certification for Ford in Detroit...

Aftermarket add-on electronics, not so much...
 

simonbramble

Active Member
I have a dual lighter socket to usb converter and if I charge my phone with it I can't listen to am radio in weak signal areas.
I have the same with FM radio. In my 5 series, my USB adaptor obliterates all but the strongest stations. The only one that does not cause a problem is the dual USB metal canned adaptor. That works perfectly - keeps the noise internal
 

MikeMl

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I have the same with FM radio. In my 5 series, my USB adaptor obliterates all but the strongest stations. The only one that does not cause a problem is the dual USB metal canned adaptor. That works perfectly - keeps the noise internal
I have dealt with this issue running 14Vdc input to 5Vdc USB adapters in various airplanes. There the RFI is a bit more critical than just not being able to listen to music....

The pilot/airplane forums I hang out on are full of anecdotes about USB adapters interfering with aircraft VHF Com and Nav... The are lists of USB adapters to avoid, and a few known good ones that do not cause interference.

The reason I hate the Chinese crap E-Bay step-down DC-to-DC converters so much is because they obliterate the entire radio spectrum from ~100kHz to hundreds of MHz.
 

kinarfi

Well-Known Member
no criticism, no complaints, just my observation, but this thread sure got of what the OP asked for, but then I haven't seen the OP come back anyway.
I didn't realize that switch mode stuff so noisy, but then, I never listen to AM radio and I haven't flown since I crashed my plane in 2006 and I think these switch mode devices have proliferated since then, please, carry on, interesting stuff.
For the OPUntitled.pngtry this if you don't need too much current, use a LM350 though, same thing with higher current rating.
Jeff
 
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dr pepper

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I have a little interest in Vlf, thanks to modern power supplies I have to do that well away from buildings & life.
 
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