555 driven relay causing issues with power loss


Joined Aug 1, 2013
Not only can you eliminate a transistor and other parts, you can eliminate the 555.

NOTE: This schematic is based on the TS information *at this time*, which is missing a lot of details. For example, depending on the relay coil characteristics, Q1 might have to be a small power transistor, small power darlington, or small power MOSFET (which eliminates R3). Hmmm ...

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Joined Aug 1, 2013
Based on the previous schematic, here is an all-MOSFET solution. The large Vgs range eliminates the zener diode that was preventing reverse breakdown, and a MOSFET doesn't need a gate current-limiting resistor. Not counting the c/l and the relay, the original schematic had 48 component pins. This has 16. R3 might still be needed, but that is a TS secret.



Joined Nov 6, 2012
This is the most ridiculous Tread I've ever seen, nobody knows any details/specifications for ANYTHING.

Lets start at the beginning ......
TS ........... I have an extra output channel on a Generic Remote Control Receiver,
that I would like to use to operate the Power Trunk Release Motor on my Car,
and I don't know how to measure its Output, and I don't have any documentation for it.
I installed a Trunk Release Motor from a Car that had that option factory installed,
and I have no idea what the original factory control scheme for the Motor was.
I successfully copied a Circuit that I saw in a Car Forum that I thought might work,
and amazingly enough, I didn't start a fire, or smoke any components. (yet)

Let's start-off with some requirements ..........

The Trunk Motor absolutely has-to-have Limit-Switch(es) built-into it.
It is not feasible for the Trunk Motor to function reliably without Limit Switch(es).

Find out which Connector Pins on the Trunk Motor are connected to the Limit-Switch(es).

There should also be a Switch that detects when the Lock-Pin on the Trunk-Lid is
in contact with the Latch Mechanism, which is moved up-and-down, by the Trunk Closing Motor.

And, (a) Limit Switch(s) that indicate(s) the end-travel-points of the Opening/Closing Mechanism.

Most likely,
the Trunk Opening Springs need to be adjusted to insure that when the Trunk Latch is released,
the Trunk Lid Pin will separate from the Trunk Latch Mechanism and
cause a Limit-Switch to either open or close.

Until the details of how the Car Manufacturer designed the Trunk Motor to operate
are established, everything else is just a massive waste of time.

The second thing that must be established is the Output of the ""c/l"" (what ever the hell that is).

We have now gleaned that this is a generic Chinese Remote Control Receiver.

The most common Output Type is an "Open-Emitter" Transistor Switch to Ground.

To establish exactly what type of Output this actually is,
it would be best to use a Cheap "Analog" Multi-Meter, available at any Auto-Parts Store.

With the Meter set to the ~15VDC Range,
probe the Receiver's Output to see if it has an internal "Pull-Up" Resistor.
If ~12V is being detected in any Mode, then the Receiver has a built-in "Pull-Up" Resistor,
( this is a Bonus, but not a requirement ).

If NO Voltage is detected in any Output Mode,
then there is no "Pull-Up" Resistor, and one must be added to the Circuit.

With no internal Pull-Up Resistor.....
A safe guess is that the Output can "Sink" at least 30ma of Current,
therefore, a ....... ( 15V / 0.03A = 500-Ohms )
500-Ohm Resistor will be the first part in the Circuit.

Then the second part in the Circuit will be a P-Channel MOSFET.

This may very well be the entirety of the required Electronic Parts for this Project.

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