12VDC Pulse in ---->12VDC Steady out

I am installing side view mirror cameras along with my rear view camera into a bus I own. I have the cameras, the splitters, the tft screen ect.

What I didn't think of is, I need a steady 12v to keep the camera activated and therefore the screen on while turning/changing lanes. Simply splicing into the turn signal light wiring produces a pulse, which is useless.

I'm comfortable creating a small PCB that simply takes the 12VDC pulse and converts it to 12VDC steady. I assume the use of a capacitor in some respect. But how. I want the camera to switch off within a second or two of the last time power is present in the 12VDC pulse. Basically a wire in and a wire out board.

So, unless anyone has any ideas - would this setup work.....
splice 12v light wire--->dieode---->capacitor---->voltage regulator--->power into camera?

I am NOT an electrical engineer by a LONG stretch (pilot/nurse). I like to tinker and do some basic Arduino stuff.

HELP

This is very unlikely to work. The voltage during the 'off' part of the pulse will decay very quickly as the camera takes current and it won't work properly.

Run an extra 12v wire.

sorry

Allan

Why do you not use a 555 or NE555 timer chip. It will run well on 12 Volts and is extremely cheap. It requires just a few components (resistors, capacitors).

Set it up as a monostable vibrator. A short input pulse can give you an output pulse from milliseconds to many many seconds - even minutes.

This is probably the best documented chip that has ever been built, decades ago. It still is one of the most sold chips on this planet. It is good and cheap.

Hi,
Are your mirrors electric adjustable type.
If so, check that you don't have a constant 12V supply there for the motors.
Most cars switch gnd to power the motors.

Tom... :slight_smile:

Why do you not use a 555 or NE555 timer chip. It will run well on 12 Volts and is extremely cheap. It requires just a few components (resistors, capacitors).

Set it up as a monostable vibrator. A short input pulse can give you an output pulse from milliseconds to many many seconds - even minutes.

This is probably the best documented chip that has ever been built, decades ago. It still is one of the most sold chips on this planet. It is good and cheap.

Quite.

But how does this help the OP's problem? He wants DC out of pulses, not the other way round.

Allan

A monostable vibrator will ...

When you enter a house and press the light button, usually the light will automativcally turn off after a couple of minutes.

This might not be true if you have your own house.

A short press/contact will turn into a longer signal.

This is the job of a monostable vibrator.

Most circuits doing this today use a 555 chip or the 555 functionality integrated into another chip.

MONO means ONE stable state. No vibrations at all.

Rather than split AFTER the signal relay...why no simply split from the indicator stalk or close by.

If you really want to get fancy an Arduino will do the trick.
Simply read an incoming pulse and start a timer on the Arduino to operate another relay for the camera.
You could even incorporate a pot to adjust the timer on the fly.

Or possibly an alternative is to consider the two variants of a one-shot -

Retriggerable One-Shot, or

Non-retriggerable One-Shot

I'd go with the RETRIGGERABLE version with a short time-constant - so the turn signal pulses keep the camera supply on, then when the signal stops, the period times-out.

There are a million circuits on the net - often based on 555/ 4047, 74LS121 and 74LS123 TTL chips.
Retriggerable one-shots

Hi,
Can you check and see if the pulsing 12V with the indicator is 12V when indicator is ON and 0V when OFF?

If gnd switching you will see 12V when indicator is OFF and 0V when indicator is ON.

Tom.... :slight_smile:

The OP wants to use the 0/+12 pulses sent to his indicator light as a 12v continuous power source for his camera. And unless it takes a small current or his storage capacitor is very large the voltage drop during the 'off' part of the pulse will be large and the camera will stop working....

and I'm not sure how his indicator driver will take to having a few mF to drive as well as the indicator. The inrush current would be large.

could he tell us how much current the camera takes? And over what voltage range it will work?

There isn't a continuous supply - whether the +12 or 0v is switched by the indicator driver..

Hence my comments

regards

Allan

ps OP - since you'll have to run a signal lead from the camera anyway, what's so hard about running an extra supply line?

Hi,
Also if the camera is only going to be on with the indicators, how long does it take for the camera to boot and start recording?

Tom... :slight_smile: