12v steps in a 24v bus

[El Gringo]

I am part way through installing electric steps in our old bus, the original steps being to big a step up at a time, so it's now down to a more manageable height.
They have an automatic retract feature the triggers when the ignition is turned on.
Of course the ignition is 24v, hence the problem.

My solution is to use a relay, so that the trigger from the ignition can switch the 12v wiring.
Not sure if I should use a 12v relay or a 24v one, or even if my idea is actually workable.

Would really appreciate some comments as to this solution or if there is a better way.

Thanx.

Before

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After

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[BruceS]

After you find out how much current it draws and for how long it takes (in or out) it's a bit of a guess.
I have a big 24V to 12V converter in the houseboat.
What do you have at present to power your 12v gear? (radio, GPS etc etc)

[Barboots]

In this context, the voltage of the relay is selected based on what is controlling it. So if the "trigger" wire is from the original bus electrics, you want a 24V one.

Do you know the current draw of the step? If it's not particularly high you may be able to get away with an extremely simple voltage divider. However if you have a 12V subsystem available, definitely use that.

Cheers, Steve

[El Gringo]

Thanx guys.
I have a pretty big OEX 24v to 12v reducer for all my 12v stuff in the front, from memory capable of 60amps.
Steps require a 25amp fuse.
Sense wire only needs a 5amp fuse though.
So the wire from the ignition should be a momentary pulse or at least just a sensor type of thing,
I will try to add the wiring diagram for the steps below.
So the main power for the step motor comes through the red wire from the voltage reducer through a fuse.

If I use a 24v relay the ignition wire goes to pin 86
Pin 87 goes on to the step sense wire
Pin 30 gets power from the voltage converter
And 85 to earth as usual.
My OEX has a common earth with the 24v and is designed to work that way.

Sound OK?

[BruceS]

"87 to step sense wire"

Not sure what that means but it's the main pos feed wire to the steps... yes.
Pin 30 is 12V in & out on 87 when the relay is activated.
You really have the choice of 12V over all or just 24V activate & 12V to power the step motor.
I guess if you're a little in doubt & don't wish to fork out $$$ for an auto elec you might just go 12V over all??

[jon_d]

put 24 volt on pin 86 and the relay will turn on.

put gnd on pin 85


put the 12 volts "battery" wire that will power the steps on pin 30.

connect the steps power wire to pin 87.

don't forget to ground the steps.

when 86 gets power, (12 volts via the ignition and converter) the relay will work and the steps will move.

[El Gringo]

put 24 volt on pin 86 and the relay will turn on.

put gnd on pin 85


put the 12 volts "battery" wire that will power the steps on pin 30.

connect the steps power wire to pin 87.

don't forget to ground the steps.

when 86 gets power, (12 volts via the ignition and converter) the relay will work and the steps will move.

Thanx Jon, that's what I was hoping I had right as was trying to explain, but not as clear as you.

Cheers.

[jon_d]

Hang on Bernie,

I think I've misunderstood things,

Q: Do you want the steps to retract automatically when the ignition is on?

OR just to work of the 24-12 volt converter?


Also, is the magnetic switch in the second diagram the open/close trigger?

I think this might help. If the house is 12 volts, then don't use the converter (ie remove from circuit) and power the steps from the house. That way, you don't flatten the starter battery.

steps.jpg

[El Gringo]

Thanx Jon,

I don't have a 12v house system, all is 24v.
This may not be ideal, and indeed it may even change in the future, but the previous owners did it this way.
So I have this overly large converter to do all the 12v stuff in the front. (it was very cheap and of very good quality)

I think therefore at this stage anyway that the converter will stay and be wired as per your diagram without the house line you have shown.

So yes, I want the steps to retract when the ignition is turned on, I will also do this with the hydraulic legs, but they are 24v so no issues with that.
But the steps have to get power from the converter.

Thanx again,
Bernie

[jon_d]

Hi Bernie,
(I have a 24 volt house and 12 volt engine. )

Then, as you've probably already realised.

In the diagram, the wire going from the starter battery to the converter is wrong .
and ignore the 12 volt house battery and wire in the diagram.


The relay will keep the house and starter batteries isolated.

jd