Re: [NTLK] Car Adapter for Newtons

From: Johannes Wolf (mp2100_at_mail-gw.estec.esa.int)
Date: Fri Feb 11 2005 - 00:14:26 PST


Joel,

this is really a simple solution and the LM317 will provide overcurrent
limitation/protection by itself.
Could you take some pictures?
The main question for me is whether they put a serial resistor in the
positive line.
This would help to limit the current as well because of the voltage drop.

Cheers
Johannes

> -----Original Message-----
> From: newtontalk-bounce_at_newtontalk.net
> [mailto:newtontalk-bounce_at_newtontalk.net]On Behalf Of Joel M. Sciamma
> Sent: Thursday, February 10, 2005 12:28 PM
> To: newtontalk_at_newtontalk.net
> Subject: Re: [NTLK] Car Adapter for Newtons

> Sonny,

> > Has anyone heard of a Car adapter for the Newton line?

> Apple did make a car adaptor for the Newt, I have one here and it looks
> nicely made for this kind of device with a car-type 3A fuse, sprung centre
> pin and solid construction.

> Opening it I see that they used the popular LM317 adjustable
> regulator chip
> in its basic circuit configuration.
> <http://www.national.com/pf/LM/LM317.html>

> I just tested it on the bench and it delivers a no-load output voltage of
> 6.99V for inputs of 9V to 15V (car batteries are normally charged
> at 14.5V)

> With a 400mA load the output drops to 6.75V

> So an adaptor with similar characteristics should be fine.

> The prices you have been given seem very high for such a simple device.

> Joel.

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