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DC to DC Converters


#1

Need to get 24v DC from 12V DC and today bought this to drive some Ph/Temperature sensors needed for project

https://www.jaycar.com.au/dc-to-dc-step-up-voltage-converter-module/p/AA0237

Max I got was 22.4 volts with 12v In
First thought, sure, it cant bee 100% effieicent, so thats why
But seeing heaps of car 12v to 24V converters out there.
Output load was only 60mA
No load same
Installed POT (5K not 4.7K, but tried shunting some reistors in to bring it down to 4.9K)

Consfused…


#2

Trimmers normally change some hundred millivolts. Take a moment and calculate:

Max in 14 volts / max out 26 volts = 0.54

Wanted 24 volts x 0.54 = 12.9 volts input

Try to input 13 volts.

Infact 22.4 volts x 0.54 = 12 volts like your input

If you cant, try on digikey something like: 945-1528-5-ND


#3

Verifying the actual voltage on some of these devices requires a suitable load. Trying using a 24V light or motor as a load, then check the output voltage.


#4

Lots of companies make boost converter ICs that generate a higher voltage output from a lower voltage input. The big guys make very affordable evaluation modules that are complete design implementations that make it easy to use their products. They’re supposed to be for engineers to evaluate an IC and then design a product that gets build by the 1000. I build very small quantities and can’t justify designing a new board from scratch so I use these evaluation modules all the time as an integral part of the systems I build. Linear Technology has a whole bunch. You can select an appropriate IC from this page and then look for the evaluation module on that specific IC’s web site

http://www.linear.com/products/step-up_(boost)_regulators

I’ve also used products from TI and they have similar web pages to help select the right IC and then identify the appropriate evaluation module.


#5

@jaycar. Love it. Spent way too many $$ in there this week (mundane things, batteries, M3 screws/washers/nuts switches). At least they’re convenient and not 12-36 days away if you order at cheaper/less reputable places ie eBay.

Nobody said that boost converter was going to be linear across the voltage range either, so you’re somewhat guessing.

  • Input voltage: 6-14V DC
  • Output voltage: 11-26V DC

Datasheet is somewhat un-techy. I was underwhelmed. I agree with Gene, grab something more robust that uses someone’s specific part that you can at least assume will be “typical”. If you’re in Sydney I might have an LT based booster that will get you out of trouble (and you can obtain on eBay, that’s where I got it from)


#6

Thanks all for comments.

Yeah I think this device just works this way, even though the product description says "run 12v devices from 6v battery"
And yes the trimmer seems to just trim down output by a few 100 mv. But no boost.
And yes I did try some different loads just in case it didnt regulate well with no load.
We have a fixed output 24v DIN mount industrial version coming in, I’ll see how that goes.
https://au.rs-online.com/web/p/isolated-dc-dc-converters/8962206/

Wish manf. would give a input vs output chart just to make things clearer.


#7

I have had good experiences with Pololu’s DC-DC converters.

In Australia:
https://www.robotgear.com.au/Category.aspx/Category/46-Voltage-Regulators


#8

Not sure what price you are willing to pay but I use these to generate ±24V for 4-20mA sensors. Max output current is 125mA per rail so more than capable to power the sensors on the 6000ft of cable I often have to supply this over.

XP Power, JCD0612D24

That is the 12V version. I use the 24V version so that I get isolated +24V and -24V for the 2 sensors.

Output voltage is 24 or just slightly over. I see anything from +24.0 to +24.3 and never below this. Voltage for the 4-20mA sensors is not so critical anyway. It does work down to +10V for the sensors I have over the longer cables. I have had success with this on 4000 meters of test cable.

They have been super reliable for years on a number of installations.