Hello, Arfa!
You wrote on Sat, 15 Jul 2006 11:51:39 GMT:
AD> ??>> Hello, Arfa!
??>> You wrote on Fri, 14 Jul 2006 22:05:09 GMT:
??>>
AD>>> ??>>>> Hello, All!
??>>>>
??>>>> Could anyone please suggest a fairly simple circuit to convert the
??>> 12V
??>>>> DC of a motor car down to 1.5V DC needed by my MP3 Player ? Any help
??>>>> appreciated.
??>>>>
??>>>> With best regards, 3T39. E-mail:
[email protected]
??>>>>
AD>>> Resistor and NiMHi cell perhaps ? Only 1.2v, and not terribly kind to
AD>>> the battery, but simple, cheap and should work ok
??>>
??>> Hhmm, A bit brutal Arfa, I see what you mean but I was hoping for a
??>> tad more sophistication :^) but thanks anyway.
??>>
??>> With best regards, 3T39. E-mail:
[email protected]
AD> Agreed, but you did say that you wanted it simple. All of the solutions
AD> offered further down, which make use of a linear regulator, such as the
AD> LM317, are very inefficient in terms of heat produced. My thinking with
AD> using the NiMH cell, was that the series resistor could be dimensioned
AD> to give a very light trickle charge to the cell, of only a few mA. This
AD> sort of scheme is common in cordless phones, for instance, and doesn't
AD> seem to do the battery packs too much harm - you generally get 2 - 3
AD> years reasonable service from them. The current to run the MP3 player
AD> would then be provided basically by the cell. When the player was out
AD> of use, the cell would continue to be gently charged, ready for your
AD> next journey. Simple and reasonably efficient ?? There is an added
AD> advantage in that the cell provides a fairly low impedance, so will
AD> tend to absorb any transients on the line from the vehicle's electrical
AD> system. To be sure, you could always 'complicate' the circuit, by
AD> adding a C of say 0.1uF across the cell. Between that, and the
AD> relatively high value of the charging resistor, just about all spikes
AD> should be slugged to the point of no consequence.
Yes I did say simple Arfa, and I understand what you say. You're quite right
about it, and I'm thinking now I might give this a try, I thought around
800R 0.25W what do you think?
Can I mention your name if I set the car on fire? :^)
Also I'd like to thank everyone who took the time to write down your
thoughts on this
Much appreciated !
With best regards, 3T39. E-mail:
[email protected]