hiroc said:
I have panasonic miniDV camcoder fixed in my car,
I need 7.9V to power camcoder from 12V car battery,
and I need two led diodes, first turn on when camcoder have 7.9V,
and another when camera start recording which I turn on with remote
control
I need circuit for this!
Thanks all!
Try this (view in fixed font or M$ Notepad):
|
| VCC
| 1N4 + ______
| B+ 002 ___ | | | 8V+
| o->|-|___|-o-----o---|78M08|---o---------o----o---o
| 2.2 | +| |_____| +| | |
| /-/ --- | --- .-. .-.
| 6PKE18 ^ --- | --- | | | |1.2K
| o | 10uF| | 10uF| 10K| | | |
| B-| | | | | '-' '-'
| === === === === === | |
| GND GND GND GND GND '-----o |LED1
| | | V~
| .--------------------' .-. -~
| | | | |
| | VCC 18| | |
| | + '-' |
| | VCC LED2| | |
| | + V~ === |
| | |\| -~ GND |
| '--|+\ ___ | |
| | >-|___|---' |
| .--|-/ 2.2K .-----o---o
| | |/| | | 8V-
| | === | .-.
| | GND |0.22| |
| | 1/2 LM393 | | |
| '-------------------------' '-'
| |
| ===
| GND
|
(created by AACircuit v1.28.5 beta 02/06/05
www.tech-chat.de)
All of these components are easily available at Mouser.com for a few
bucks.
Here's how it works: The diode, 2.2 ohm resistor, and Transzorb help
protect the rest of the circuit from load dump or reverse polarity.
Your 78M08 will give you 8V (close enough -- even if it's a little
high, that would be similar to a fully charged battery). The trick is
the current sense resistor on the 8V return line. A small voltage is
impressed across it, which is sensed by the comparator. The comparator
output will turn on the LED if total current (LED + camcorder) goes
over 60mA or so.
Note that you will need high intensity LEDs for this circuit, because
the LED current limit resistors are set for 7mA each. If you want to
use standard LEDs, and you get false triggering, bump up the 18 ohm
resistor a little bit.
This isn't the most elegant circuit, but it will work OK and be safe
for your camcorder. Be sure to remember that the voltage source for
the camcorder should be isolated from car chassis ground -- the
negative is not at ground potential.
Good luck
Chris
