building circuit for automatic truck steps

I own a 2007 dodge ram mega cab and ever since I saw a set of automatic power step like the ones from AMP Research, I have wanted to put them on my truck. However, they cost over 1200 dollars without installation and being fairly fabrication savvy, I believe that I can make a set of automatic steps for much cheaper using the mounting brackets from my existing side steps. I figured out most of the details but I am completely illiterate when it comes to electrical circuits and relays. I am going to use a linear actuator on either side to raise and lower the step and power them by tapping off the door ajar sensor the same as the AMP research steps. The only problem is the polarity needs to be reversed on the actuators to make them retract and ideally there would be a slight time delay between when the door is closed and the steps retract. I would also like to be able to turn the steps off or manually extend and retract the steps from inside the truck. In addition, if possible I would like some sort of sensor switch or circuit breaker to act as a safety similar to the sensors on a garage door but this is not necessary if it is too complicated. Any advice, information or expertise would be greatly appreciated. Thank you

Use actuators with internal limit switches.

Here's an old thread for a similar setup using actuators. I don't know where the guy got the reversing relay in that thread, but there's a P/N in his post. You can also use 2 cube relays to do the reversing. Adding a capacitor and resistor will accomplish the delay.

The safety thing for "overload" is more complicated. I don't know how to do it other than current sensing, which is way above my pay grade.

There's some ideas. If you actually do this, come back and we'll help you with the details. The key for now is to find actuators with internal limit switches.

I have already found actuators with internal limit switches. here is a link to the actuators I am considering using although my design can really use any length actuators... thanks for the info.
https://www.progressiveautomations.com/linear-actuator-ip66

Ref. the safety delay, could you use something like a DEI 535t or 2 X 529t window closers to control the steps, this would give you the timing and safety cut out in one package assuming it's OK with the current handling.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

You could go with one 529t per side, just separate the orange and ORANGE / black trigger wires to make a 529t bi-directional for each side.
If OK with the current capacity required that would solve our OP's understanding problems with electrics.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

KPtechnologies offers a prebuilt running board controller. It has (2) door pin inputs per side (for front and back door). It is time based with an adjustable output that can be dialed in for your steps, and then modified as the motors start to slow down over time.

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Kevin Pierson

Nice one Kevin.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thank you Kevin that looks exactly like what I need. Will they work with a linear actuator with only two wires?

All PM motors have "only" two wires.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Explanation, both wires either sit on ground (NEG) (90%) or 12v+ (POS).
One wire changes polarity to move then reversed to change direction.
That rule applies to all DC permanent magnet motors, linear actuators, door locks window motors etc.

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Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.