Iggy

A while back I mentioned that I had an idea for a relay circuit for the motorized hatch lifts. many of us have had them jam at either the full up or down positions.
OSO memeber Krakmeup asked if had gotten to it yet. Well, I have and here it is.

The circuit won't be cheap to build. The relays alone cost 66.00 each times 4.

I know my logic may be hard to follow but if you have any questions, feel free to ask.

Poorsche

I bought one from Rex Marine for about $30 ifI remeber correctly--

Poorsche

Iggy

There are kits for installing relays into the power circuit, but non that offer opening and closing limit switches. I've had my boat for 4 seasons now and had to remove and repair the lift motor 5 times.
Don't know about other brands but on my Formula the power cables for the lift motor runs from the batt to the instrument panel then back to the lift motor (about a 30ft+ trip). The long distance causes all kinds of troubles.

BTW I know the sketch is rough. I didn't have a whole lot of time to work on it. I will do up right.

Audiofn

Iggy first of all good idea. If you do not mind can I make some suggestions on your design? Hope so cuz hear they come

1) MAKE SURE this is NOT mounted in the engine compartment unless your relays are coast guard aproved!!! You can mount them just outside but lets stay safe.

2) Use a ground at rest relay and you will be able to get that down to 2 relays. Plus it is safer if you have a relay stick you will not feed power possibly down both sides causing a short and blowing your motor.

Jon

Iggy

These relays are not Coast Guard approved, but they are explosion proof. They have no moving or spark producing components. They are totally encapsulated in potting compound.
As for them sticking engaged, it is possible, but I can't recall the conditions necessary for it to occur.

Ground at rest relay? I'll have to look into that. Not really sure how it works.
You sure something like that would work in a circuit where the polarity has to be reversed to drive a motor? Give me an example.

I thought about having the micro-switch cut the power going to the lift motor but finding one to handle the current may be hard. It is easier to cut the power that energizes the relay.

BTW, thanks for the input. If I didn't want anyone's opinion I wouldn't post the idea.
The OSO family has a wealth of knowlage and expertise. This is a hell of a way to perfect an idea.

vonwolske

Usually those lift motors for hatches, power windows and even some hydraulic motors are case grounded and have two separate power leads going into the motor. If that is true with your motor, you are way over killing on the controls.
These motors are actually two separate electrical windings internally and to the unannointed mind looks like you have to have one wire polarity to get it to go up and then reverse both wires to get it to go down. Not true.
You must ground the motor case as that is common to both windings. Then you independently energize either wire to get it to stroke. Do not do both at the same time or it will stall and burn up.
So a simple heavy duty single pole, double throw switch, with spring return to center off position will work. This is the same as the rocker switch for your car window.

There are automotive single pole double throw relays available and if you put it where there are no explosion hazards, like under the rear seat, then you should be ok. You aren't pulling enough amps to warrant a starter duty relay, e.g., 100 amps.

The motor is probably 15 amps max. and switches can easily hanle that.

Personally, I would not use the relay approach if the switch option is so available. Save money, space, complications.

Most electrical problems on boats are corrosion related, so use of tinned wire and marine duty switches really helps.

email me if you need more input.

Jim

Wally

iTrader: (1)

Audio.....you can make a regular relay a "ground at rest" just from the way you wire it....

Iggy, i posted this up a while back....dont remember what post it was on but this diagram shows how to wire up a regular Bosh type auto relays to work. Only takes two relays and you can incorporate your micro switches into the mix to make your limits.....just add it on the 12v+ supply line going to the relays

Wally

iTrader: (1)

they way i have it wired works best because you dont have a long run on 12v going from the dash all the way back to the relays in the engine compartment.....plus teh added benefit of saftey if the line ever gets pinched you wont have to worry about it causeing a fire .......now that i think about it and look at my drawing, it would be better to add the micro switches to the ground wires of the relays.....you know the whole pinch/fire/short thing again!

Iggy

The Wagner electric screw lifts, as used on the vast majority of our boats, does not have a case ground. There are only two 10 gage wires leading to the electric motor. Polarity must be reversed in order to change direction. Follow link Screw Lift and look at wiring diagram.
The factory wiring on my Formula has high amperage power running from the battery to a switch on the instrument panel then all the way back to the screw jack. Polarity is reversed at the dash switch. This long distance run causes the screw jack to run slower than normal. Many OSO members have complained about how slow their engine hatch opens. The long distance that the power has to travel is the cause.

The relay I propose to use has only four connections.
Two are for 3.5-32V DC (28mA max) to switch the relay off and on.
The other two connections are for power(or ground) in and then out to the load.
That's it.

As for pinches and shorts....well, we all know enough to install circuit protection devices.

The instrument panel switch I plan on using is a Mil Spec type that is sealed and weather proofed.

mcollinstn

No need for four relays. Can do it with two.

They DO make limit switches that will handle all kinds of current. Honeywell makes them under the "Microswitch" brand name.

I've got a box of actuators with BUILT IN limit switches in them that I bought off EBAY from a university robotics program. They do NOT have enough ass to handle a Formula hatch, by a LONG shot (dang those things are heavy), but they are cool units.

Don't know if you've thought about it, but you can change the dash switch to a 3 position (non momentary) switch if you use limit switches and relays. That way, you flip it up, it stays up, the hatch goes up by itself and stops. Handy. Same for down.

I installed one of these on a Crownline and on a Cobalt and they both turned out magnificent.