+/- 12v to 10v DC DC converter
Discussion
I have a military radio which requires a good 10 - 10.5v power supply with a standby 10mA, Receive 30mA and transmit maximum of 1.8A draw.
I wish to use car batteries and smaller 12v type batteries, and am looking for something I can place inline which will keep a constant 10v out, and can handle the 13 - 10v fluctuation on the incoming side.
I have been looking at DC - DC converters and "buck" inline but nothing seems to be what I need.
Any pointers please would be a tremendous help.
I wish to use car batteries and smaller 12v type batteries, and am looking for something I can place inline which will keep a constant 10v out, and can handle the 13 - 10v fluctuation on the incoming side.
I have been looking at DC - DC converters and "buck" inline but nothing seems to be what I need.
Any pointers please would be a tremendous help.
How often will the input drop as low as 10v? That will be your main issue as in normal droppers there is always a delta between input and output. You would either need to find a 2 stage converter or stack a step up and a step down converter with a cap in between
Something like a step up to 24v, some capacitors then step down from 24v to 10v would give you a clean stable output at your range of inputs, at the cost of.abit of efficiency. If you go for a straight dropper when the input drops to 10v the output might drop to 8 or 9v with some ripple, it depends if that will harm your radio.
Something like a step up to 24v, some capacitors then step down from 24v to 10v would give you a clean stable output at your range of inputs, at the cost of.abit of efficiency. If you go for a straight dropper when the input drops to 10v the output might drop to 8 or 9v with some ripple, it depends if that will harm your radio.
Edited by OldGermanHeaps on Saturday 5th April 11:02
dmsims has a good suggestion.
Why are there fluctuations on the "incoming" side? Will you be attaching a charger to it? Or is it a car starter battery? Starting an engine can play havoc with the voltages.
If it's doesn't need to keep operating through charging/starting operations then it should be easier to keep it stable.
Why are there fluctuations on the "incoming" side? Will you be attaching a charger to it? Or is it a car starter battery? Starting an engine can play havoc with the voltages.
If it's doesn't need to keep operating through charging/starting operations then it should be easier to keep it stable.
JABB said:
I have a military radio which requires a good 10 - 10.5v power supply with a standby 10mA, Receive 30mA and transmit maximum of 1.8A draw.
I wish to use car batteries and smaller 12v type batteries, and am looking for something I can place inline which will keep a constant 10v out, and can handle the 13 - 10v fluctuation on the incoming side.
I have been looking at DC - DC converters and "buck" inline but nothing seems to be what I need.
Any pointers please would be a tremendous help.
The issue here is the minimum input voltage being allowed to drop to 10V.I wish to use car batteries and smaller 12v type batteries, and am looking for something I can place inline which will keep a constant 10v out, and can handle the 13 - 10v fluctuation on the incoming side.
I have been looking at DC - DC converters and "buck" inline but nothing seems to be what I need.
Any pointers please would be a tremendous help.
IF you can keep the input voltage above about 11.5V, it becomes a lot easier.
Depending on the sensitivity of your radio to supply-borne interference you might use a Low Dropout or LDO linear regulator, or you might be fine with a DC-DC converter such as you can get from ebay for a fiver.
I would probably try the dc-dc, as I have one on my desk, if supply noise is a problem, maybe it can be filtered, or I'd clarify the voltages really needed and look at LDO's.
Another possibility is to power from some lithium cells.
Military stuff often works fine well outside the quoted rail requirements (but don't blame me if you blow it up...)
The only issue with a buck converter is in this application is the range of Vi includes close to the required Vo. Off the shelf buck converters dont like to regulate properly when Vi is less than 1 or so volts above Vo and become unstable and introduce ripple on the output.
Ripple on supply voltage to radio transmitters designed to operate from batteries without proper filtering can cause unwanted harmonics.
If those harmonics cause high swr on the output to the antenna it can damage the final output stage on the transmitter.
Ripple on supply voltage to radio transmitters designed to operate from batteries without proper filtering can cause unwanted harmonics.
If those harmonics cause high swr on the output to the antenna it can damage the final output stage on the transmitter.
How picky is the radio over its 10V?
There are loads of wide input DC DC converters that will do what you want and give 12V, which can usually be adjusted down by 10% or so giving 10.8V.
Have a look at Traco and XP products on the RS Components website.
Edit:
https://uk.rs-online.com/web/p/dc-dc-converters/17...
This looks way more powerful than you need but at first glance will do what you want.
There are loads of wide input DC DC converters that will do what you want and give 12V, which can usually be adjusted down by 10% or so giving 10.8V.
Have a look at Traco and XP products on the RS Components website.
Edit:
https://uk.rs-online.com/web/p/dc-dc-converters/17...
This looks way more powerful than you need but at first glance will do what you want.
Edited by blank on Saturday 5th April 22:35
dmsims said:
That looks good. When it says "Output voltage: 1.2-35 V (continuously variable)" Can I set this at 10v no matter what?JABB said:
dmsims said:
That looks good. When it says "Output voltage: 1.2-35 V (continuously variable)" Can I set this at 10v no matter what?What you need is a buck/boost regulator. These use a topology which provides a set output for an input both above and below the set voltage.
Amazon clinky
jet_noise said:
As OGH says above there will be a minimum forward voltage/differential 'twixt Vi & Vo/drop out voltage (similar terms for the same thing) which your specification will breach. I found a datasheet which suggests a minimum of 0.3V but not a max against which you should be designing. When breached outputs tend to then track the input with a constant drop, also typically noiser too.
What you need is a buck/boost regulator. These use a topology which provides a set output for an input both above and below the set voltage.
Amazon clinky
That's fair comment, but I suspect it's easier to achieve what the OP actually wants by 'clarifying' the requirements.What you need is a buck/boost regulator. These use a topology which provides a set output for an input both above and below the set voltage.
Amazon clinky
A 12V lead-acid battery should not be going below 11.5V, except maybe on a car while cranking. Do you need the radio while cranking?
Various solutions could work, what's best depends on the exact requirements, budget and the Op's ability to faff with electronics.
OK, so thinking on about this project, I have a number of Milwaulkee batteries, 5 and 6ma/h
Would one of these be a better option with a buck? More steady power
https://amzn.eu/d/i5dS7TF
Would one of these be a better option with a buck? More steady power
https://amzn.eu/d/i5dS7TF
dmsims said:
Thinking out loud, why do you need to use batteries?
How do you mean?This is a mobile radio. https://www.combatradio.org.uk/prm4700.htm
The battery packs I have are all old and no longer any good. I want to modernise.
JABB said:
How do you mean?
This is a mobile radio. https://www.combatradio.org.uk/prm4700.htm
The battery packs I have are all old and no longer any good. I want to modernise.
Cells no good or enclosure? Is opening up the pack and seeing what cells are inside an option. They're NiCd right, so pretty common chemistry. This is a mobile radio. https://www.combatradio.org.uk/prm4700.htm
The battery packs I have are all old and no longer any good. I want to modernise.
JABB said:
How do you mean?
This is a mobile radio. https://www.combatradio.org.uk/prm4700.htm
The battery packs I have are all old and no longer any good. I want to modernise.
Right got itThis is a mobile radio. https://www.combatradio.org.uk/prm4700.htm
The battery packs I have are all old and no longer any good. I want to modernise.
Make a pack from 18650 cells ?
https://www.fogstar.co.uk/collections/batteries
Gassing Station | Computers, Gadgets & Stuff | Top of Page | What's New | My Stuff