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Anyone here ever built a voltage doubler using caps and diodes. I dont need a double but would like 18vdc from a wave bridge rectifier that is putting out 10-12vdc.
 

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We used to build them. Now just go to ebay or Amazon and search on buck boost circuits. You can't build them for what these cost.

Pete
 

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So I bought one of those DC to DC inverters on ebay and the criminal seller ripper me off. They didnt work and he said they will not work with model train power supplies. I have a filtered MRC tech 7 and it looks pretty straight on a scope.
 

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it -should- work, i don't have the exact same unit, but i had a mrc 1300 and it worked on a DC-DC converter [not sure who i got it from anymore though ..]
 

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So I bought one of those DC to DC inverters on ebay and the criminal seller ripper me off. They didnt work and he said they will not work with model train power supplies. I have a filtered MRC tech 7 and it looks pretty straight on a scope.
Pic or link to the inverter please. And what "doesn't work"? No output at all, can't adjust the output, etc.
 

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Even with the cap, it sucks the power supply to mv. Remove the board and volts are back. Boards suck, I will just leave him bad feedback.
 

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Even with the cap, it sucks the power supply to mv. Remove the board and volts are back. Boards suck, I will just leave him bad feedback.
A link would be helpful to know which model / vendor to avoid.

I have a couple posts in another forum with a member that can't adjust his boost converter - it's stuck at 12 V no many times he turned the trim pot. And that was becuase he set the display to measure input voltage rather of output voltage :)
 

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Discussion Starter #11

Pretty straight forward, input+ input- and 5vdc to run - turn pot screw to adjust. Chinese QAC=1:10
 

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FWIW, none of these are actually good for anything close to the advertised current. The regulator is rated for that, but that's assuming a pretty hefty heatsink. To inject a little reality into the discussion, here's a graph from the the datasheet for the regulator.

549711


Remember, for a boost regulator, the maximum current rating will really be the input current as the output current will always be less. Also, the chip is less efficient at lower input voltages, and so it's output will be lower power.

Here's the full datasheet: XL6019 Datasheet.pdf

If it's running at 90% efficiency, it will pretty quickly get to it's internally power dissipation shutdown long before it gets to the quoted current output.

 

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So I bought one of those DC to DC inverters on ebay and the criminal seller ripper me off. They didnt work and he said they will not work with model train power supplies. I have a filtered MRC tech 7 and it looks pretty straight on a scope.
Was the MRC's output under load (0.5+ amps) when It looked straight on the scope?

The spec.'s on the MRC's DC variable output is 20 VA. That means your boost inverter can't output more than 18 VA before the MRC exceeds it limits (there no free lunch ... eh, power). At an 18 V output you're limited to 1 amp before the MRC shuts down.

What's the application?
 

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Discussion Starter #17
I also tried a 9.6 battery out of an r/c car. That should have been enough va. Still nothing. Chinese junk.
 

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FWIW, none of these are actually good for anything close to the advertised current. ...
+ 1.

On a different note, I'm using the pictured buck regulator (LM2596 chip) with an input voltage of 35 V at an output of ~13 V @ 2.5 A driving a 5 meter, 12 V LED strip. The difference between input and output voltage at that current generates a lot of heat. I used the pictured self-stick heat sinks (14 mm x 14 mm, ~$1 for 10) on the chip and the inductor. I've run it over an hour at a time with no issues but it still gets to hot to touch :)

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