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Help: Design a transformer from Car Battery to 4.5v level?

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TheMatrix65

New Member
I have a battery-operated Trafficmaster which tells me of any traffic jams 12 miles ahead of me, etc. This device uses 3 x AAA batteries which I usually replace approximately 1-2 months, depending on how often I drive my car. Now, I would like to wire it "permanently" to a car battery by way of a transformer to downgrade 12v into 4.5v with the equivalent amperage as those of 3 x AAA batteries. Could anyone design such a small transformer that would do the job so it would save me buying batteries all the time. The design (pcb and components) would need to be small enough, say 6cm by 3cm by 6cm, overall? (Those are approximations, as I am installing it near the courtesy light compartment (it has a permanent 12v feed as well as ground feed)).

Much appreciated.
 
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rmyers2051

New Member
A simple voltage regulator such as Radio Shack #276-1770, which is in reality, a "7805 regulator" will do nicely. Simple point to point wiring and potted in epoxy using a matchbox would be a snap!
 
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charles hafer

New Member
4.5 volt transformer

:lol: could use a 4.7 volt zener and one resistor too. i guess the resistor value to be approximately 510 ohms.
 
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bogdanfirst

New Member
u can use a 7805 or 78L05 depending of the power it consumes...witch generates 5V then conect a diode after it maybe a Ge one to have a dorop of voltage of about 0.4V(Ge) or 0.6 V(Si) thats if 5 volte is 2 much...
:roll:
 

crutschow

Well-Known Member
Most Helpful Member
10 years and no "Thank you" from the original poster yet. Is the snails pace normal?
No. And it's also not normal for people to reply to 10 year old posts. :rolleyes:
 

simonbramble

Active Member
I had exactly the same problem with my traffic master and that was 10 years ago. The digital electronics works perfectly at 3V, but the RF stops working at 4.5V, meaning 3AA batteries does not get you much life.. and you end up throwing the batteries away when the are still nearly new. Crap design.

A MAX738A cured the problem and continued to work 100k miles later
 
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