fire dept 5.4 volts dc from 12 volts dc

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Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=120779
Printed Date: May 01, 2024 at 5:18 PM

Topic: fire dept 5.4 volts dc from 12 volts dc

Posted By: greenham
Subject: fire dept 5.4 volts dc from 12 volts dc
Date Posted: March 17, 2010 at 4:10 PM

I am new here with a very specific need. I am a volunteer firefighter and a new device is on the market (https://www.apollowireless.com/shtml/category/FullPath/2;1722/id/1722.html) that is a large alpha numeric pager that can be used on a 120v AC desktop. This is a unit has a large display. I emailed the company asking if they had a 12 DC version that could be used in our fire trucks. I got the following response.

Our TP200 pager needs 5.4 Volt DC power, you can simply purchase an adapter
from Radio Shack that transfers the 12 Volt DC to 5.4 Volts, nothing else is
needed and this is a perfect product for dash mount trucks or buses
Therefore this unit is compatible with 12 Volts DC power

My request for your help is where can I find such an adapter. Going to Radio Shack was a laughable ordeal. If it can't be looked up by a part number there isn't anyone there that has any knowledge.

Replies:

Posted By: oldspark
Date Posted: March 17, 2010 at 6:32 PM

Easy to solve - email the company to get the part number and price....
Whether from RS or others.

You should also find out what range is tolerable. Nothing is "exactly" 5.4V, so is it 5-6.5V, or 5.4V-6.5V, or 5-9V etc?
And what its current demand is - both backlit and not.

I love their "transfers the 12 Volt DC to 5.4 Volts".... it's called conversion, or reductions, or transform... but "transfers"??!!
But IMO that matches their "this is a perfect product...".

There are settable cig-socket DC supplies but I couldn't find in my search (I'm on dial up at the moment). From memory they are ever 1.5V - eg 4.5, 6, 7.5, 9V etc outputs.
And lots of 12V-5V supplies (USB, iPod) etc that may be 5.4 etc in reality.

The pager uses 3 AAA rechargeables as "backup". That means 3.6V (3x1.2V; or 3x1.5 = 4.5V if non-rechargeable AAAs).
But if "backup" means data backup or operational backup.... But it's probably only data backup (especially if backlit - that would discharge the AAAs much faster)... otherwise it seems like any 5V supply would suit.

And if all else fails, there is the almighty 317K chip that could be set for "exactly" 5.4V. But that's another story... (available typically with 100mA & 1.5A outputs).

Remember, whenever anyone says how easy it is to get or do, then surely they can do it - even for a few buck$ extra.... (LOL)

Posted By: anonymous1
Date Posted: March 17, 2010 at 10:54 PM

Good post oldspark.

In trying to interpret the company's jibberish, it occurs to me that it requires a "minimum" of 5.4v and probably runs just fine at a solid 6v.

When you email the company, ask them what the maximum current usage is in operation.

The best answer is probably still going to be the LM317 on a small heatsink with a very few additional parts, and you could pay some kid a few bucks to solder several for you.

Posted By: anonymous1
Date Posted: March 17, 2010 at 11:03 PM

I have a few of this type of adapter and after reviewing the product again, I think it's a low current draw.

It might be that you can buy one of these and then a USB > 5mm din plug. You would need to determine what the supply socket size it on the pager.

https://www.amazon.com/Manhattan-USB-12V-Moblie-Charger/dp/B002FC9SXG

Posted By: another-kelly
Date Posted: March 20, 2010 at 12:23 AM

i've had good luck with a product called "Hitch Hiker". it's a dc-dc converter that's fully adjustable from 1.5V-12V via the small screw or pot on top of the unit. just connect your meter and set it at exactly whatever voltage you need. just google: hitchhiker dc adapter