What might make it dangerous is a shorted 317. Don't know if the sender can survive the heavier (~.1 to > 1 amps) current that would result. For example worst case:
14.4 volts, 317 shorted Vin to adj, sender at 13 ohms: > 1 amp best case: 317 shorted Vin to Vout, 14.4 volts, sender at 100: .096 amps. The above is purely a guess at what Fred might have in mind.Ed
See updated schematic at
I added the 240 ohm resistor and the damping circuitry.
I also added a capacitor on the output of the LM317L to maintain stability (after a SPICE simulation revealed an oscillation), and corrected the offset bias resistors so the output behaves as desired.
I have a similar question but my factor level unit reads 13-75 ohms and the new gauge requires 33-240 ohms. Can a circuit convert those readings?
Neat!
Yes- you might first try a simple resistance multiplier x3. It requires a negative supply, and works more or less depending upon how much voltage the meter wants to see and how much current it delivers: View in a fixed-width font such as Courier.
. . BATT . | . | . METER . CKT . | . | . +-------------------------+ . | | . | | . >| 10K | . 2N2907A |-----/\\/\\-------+ | . /| | | . | | / . | | 200K . | V+ | / . | |\\| | \\ . +------------|+\\ | | . | | >--+ | . | +--|-/ | . | | |/| | . | +---------------+ . /_ | | . \\/| V- / . SENDER / 100K . /\\ / . 13-75 | \\ . | | . --- --- . /// /// .
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