14 to 28V Converter

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kyleb

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I bought a neat Russian cockpit clock to add a retro touch to the panel of the RV-10 I'm building.

What I didn't think of was input voltage. It needs 27V and I've only got 14V available.

Is there an easy (cheap, efficient, yada, yada) way to ramp up the DC voltage on one circuit so I can use it to run the clock?
 
Do you know how much power it needs? A DC/DC boost converter will probably be the way to go.
 
Piece of cake. One small 8-pin DIP IC, one inductor about the size of a nickel, two capacitors, two resistors, and your chosen method of housing (preferably a small metal chassis to keep the nasty noisies inside). Ten bucks at the outside. I'll send you the parts if you will make it, test it, and let me use the resultant information (including photos) in a Kitplanes column.

Should be able to do half an amp for the same price. No savings in doing anything less.

I may even do a PC board for it. I get three for the price of one, so I'll send the board along if you want.

Jim
 
If it will run on 24, you can get a whole assembled device for under $50.
 
ifly4fun said:
http://m.ebay.com/itm/NEW-Booster-Power-DC-Converter-Step-Up-Regulator-12V-to-24V-3A-72W-/351927412473?hash=item51f08226f9:g:djEAAOSw2xRYR8DL&_trkparms=pageci%3Ad0519b40-d785-11e6-b742-005056b676fe%7Cparentrq%3A8a8a5cee1590a34fcc58f1a8ffbb7b50%7Ciid%3A2
Click to expand...

Whaaaa? :eek:

For 12 bucks that might be worth getting just to take it apart to see what's inside to see if it would hold up to 14/28V conversion. Plus their other top Hot Item is "New Women's Underwear Lingerie Babydoll Sleepwear Lace Dress G-string Nightwear". Sounds legit.
 
kyleb said:
Can't be much. A fraction of an amp @ 28V?
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Hmmm, so I googled "russian aviation clock 27 volts" and found several hits for mechanical clocks that use the 27V input for an internal heating element so it can operate down to -60 degrees C. Is that what you have? This could be quite the guessing game about how much power that would consume.
 
weirdjim said:
I may even do a PC board for it. I get three for the price of one, so I'll send the board along if you want.
Click to expand...

Why bother? There's hundreds of buck and boost converters littering eBay available for less than $5, shipped to your door.

By the looks of them, they're all made in the same factory in China, and various brand names are slapped on them.

Tons of teardowns and reviews of them all on YouTube, by bored electrical engineers, too... making a few bucks making nearly daily "content" for a thousand bucks a month in retirement by pushing whatever commercials we all hit Skip on at YT.

Real easy to avoid the sketchy ones, just poke the brand and model into a YT search. Someone will have a video pointing out the design flaws or saying they're reasonable.

The entire power supply has become a "jelly bean part" at this point unless you need something special in the design, or you just like laying out PCBs in one of the multitude of free layout packages.

Heck if you need ten of them, fire up Alibaba and order them even cheaper. That's what the eBay sellers are doing.
 
rpadula said:
Hmmm, so I googled "russian aviation clock 27 volts" and found several hits for mechanical clocks that use the 27V input for an internal heating element so it can operate down to -60 degrees C. Is that what you have? This could be quite the guessing game about how much power that would consume.
Click to expand...

If it is only for the heating element, I don't really care. I won't be operating it under about 20F, so the whole thread may be a moot point... I'll dig it out of the box and czech to see if it is indeed a mechanical clock with a 27V internal heater...
 
rpadula said:
Whaaaa? :eek:

For 12 bucks that might be worth getting just to take it apart to see what's inside to see if it would hold up to 14/28V conversion. Plus their other top Hot Item is "New Women's Underwear Lingerie Babydoll Sleepwear Lace Dress G-string Nightwear". Sounds legit.
Click to expand...

Just check it with all your equipment to see if there is interference. The converter and the undies as well. ALL your equipment.

Jim
 
weirdjim said:
Just check it with all your equipment to see if there is interference. The converter and the undies as well. ALL your equipment.

Jim
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Now THAT is true. Many boost and buck (they're opposite but operate on similar switching principals that make a crap ton of electrical and RF noise when done improperly) converters are hideous noisemakers.

That might be a benefit of Jim's board. He'd actually do the math to keep the switching speed used NOT a multiplier of any of the aviation RF bands, I'm sure.

Because it's not Jim's first aviation electronics design rodeo. :)

No guarantees on the $5 one from China.

I guess I didn't mention that if I were installing one in an experimental airplane it would have made a "visit" to the ham shack and bench and gotten the evil eye with the spectrum analyzer and the scope for switching frequency.

Maybe I was a little too cavalier about saying one could buy a cheap one. It's easier to buy cheap Chinese electronics if one has a little test gear lying around... just to make sure the little $5 bugger isn't doing something completely insane.

So yeah. Don't expect proper design or quality out of eBay and Alibaba junk from China. But if you can at least find your way around a multimeter and look at a board for the inductor and capacitor ratings and do a little math, you can find some screaming deals on good stuff and also find some stuff only worthy of dropping straight in the rubbish bin. At $5, no big loss.

My favorite deathtraps are the cheap USB power supplies from China that connect the shield of the USB plug to mains earth reference when charging them from the wall. Those are sure to be popular at Fourth of July parties if someone decides to charge their metal cased cell phone on a conductive surface with one while the pack is also plugged into AC and charging! Here's hoping they aren't touching the phone when they do it.

Basically anything with a true AC input and not a wall wort, that also has a USB plug on it, and was built for less than $10 in China... don't plug the device into AC power and charge it as the same time you use the USB if you value your life. Tons and tons of scary design garbage when it comes to that little "boo-boo" of electronics design. Or at least check continuity between that USB shield and the AC inputs with a multimeter. If they're connected, beware of Big Bang. :)

Of course anyone who's taken a course or self-taught on an o-scope also knows that particular "bang oops I let the smoke out" method. Same deal.

Dave over at EEVBlog covers it nicely:

 
kyleb said:
I bought a neat Russian cockpit clock to add a retro touch to the panel of the RV-10 I'm building.

What I didn't think of was input voltage. It needs 27V and I've only got 14V available.

Is there an easy (cheap, efficient, yada, yada) way to ramp up the DC voltage on one circuit so I can use it to run the clock?
Click to expand...

You need a power 'booster' so to speak. Ameri-King used to make the AK550 for this purpose. The FAA shut them down and they are out of business but I've used these converters before for this purpose and they are OK. You can probably find one on EBay for a few hundred bucks or cheaper. They made them in several different versions all the way up to 48 amps. If not Ameri-King, then KGS Electronics in CA makes a few but they are pricey since they are all TSOd.
 
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