Remote Control Boot/Trunk Release on Aftermarket Kit

[R_U_AFA]

Has anyone had any luck in getting the trunk release to work on one of the aftermarket remote control c/l kits?

The one I have, is one of the cheap chinese kits like in the link at the bottom.

My problem is that I can get the unit to pulse when pressing the boot release button, but it is too weak to trigger a standerd automotive relay (the pulse is around 0.5V, 100mA for 2seconds)

I have attempted to create my own switching circuit using a NPN tranisistor in place of a relay, but with no success, that was using the pulse connected to the transistor base. (Interestingly enough I was able to trigger the transistor just by touching the transistors base with my bare hand) but not using the pulse wire from the control unit.

Is there something I am missing?

I am a total novice when it comes to microcircuits, but I know my way around automotive wiring

https://www.ebay.co.uk/itm/CAR-ALARM-CENTRAL-LOCK-LOCKING-KEYLESS-ENTRY-KIT-SYSTEM-WITH-2-REMOTE-KEY-TECH/264066296936?epid=19023752330&_trkparms=ispr%3D1&hash=item3d7b93ec68:g:LQEAAOSwctJcASsq&enc=AQAEAAACUBPxNw%2BVj6nta7CKEs3N0qVAnOmDQ%2BKxzvzFVuT%2B00XaRQaDLwHEs3I24RHEV%2FKjDj17Ed77HMcxkfiiwY3ZUgbsf5qZ2zyjN3j2a3aHdQcBmJZtEn0Q4Nd%2BjoiEQHbvK4x6VuHkAwgCZmKOorqH%2B7FDqYxe9ROoqZOq0RuMR1VA0IyXVkvilo%2F1xVdYQRNcQgSnfBplIuM00lyfb7c45iK5rt04pz0XDXPJ5rVwlfFghLXCJ3%2Bds%2Fl4mFKOb7dfmdSYoNGjdC%2FkjLvuizxOV0BDYcWc1Kz8tLgJaWxOYGBaxiqXS0G0eF6zI97mKCgbedh10GUetKCG%2F35gDMDq1Q5eCgL1OflUl%2B4mzRWV2MwnwHbazmsSLYjLIcmZS3FeRRqQF%2BnE7XUGabU1tvqAYX8lWTNGrrDZb3LVIKawpWii7a6Z4KTvUqjsVIIff%2Fh4Hiq%2FCcI99lId%2Fz%2BIjZNQiwM3el%2BqodJZJEQqFOsBk9JPeiRYw94woyy7hp46ylzxWjcAdxKxJWjO2rAmA9QuQvLdKlDpvB2X3Utsl%2FJ74UOHMS0yasT1d%2FPeCHhcXm%2Br4qL%2BOdBtJd4Bcn8ndphQ34UqDaEQSlt63rveJiEE0UPh7bBT6l4dLBeKe47y8xjq9IJOpbaluaB1G9XnURIPwRO3znbG2c%2BMStG7vn8Ru8Uu9mHx6BJwGOd1eSMq3mbruSTjZRS0LkmEBJ3HSbNsOc7k6aKlqXqoJZBVl3wtbovaodMVBz8X1%2Fc0D%2FQir6yjad8wBo6bYf7Fd3DAv4lkk7s%3D&checksum=26406629693697114c3c224e40989138798a5b838a37

[PetrolDave]

0.5V won't trigger a silicon transistor, that needs 0.7V

[R_U_AFA]

Is there another work around? Mabey a field effect transistior?

I could probably manage to get a 0.7V pulse from the unit, but it would mean removing a diode from between the unit and transistor base, which I am reluctant to do in case I damage the control unit with too much current or incorect polarity.

[PetrolDave]

1 hour ago, R_U_AFA said:

Is there another work around? Mabey a field effect transistior?

You would be VERY lucky to find a FET that would switch with that low a gate voltage.

 

Better to look at an op-amp with an open collector/drain output then connect the inverting input to the module and the non-inverting input to a resistor chain designed to deliver 0.25V.

 

Then connect the relay between the op-amp output and 12V.

[KenONeill]

On 14/02/2020 at 17:38, R_U_AFA said:

one of the cheap chinese kits

Well, there's your problem right there; buy cheap, buy twice...