Model Boat Mayhem - Forum

Technical, Techniques, Hints, and Tips => The "Black Arts!" ( Electrics & Electronics ) => Topic started by: Garabaldy on January 08, 2009, 03:11:21 PM

Title: Is this possible
Post by: Garabaldy on January 08, 2009, 03:11:21 PM
i have a stern thruster to install but not a channel to operate it from.  What i was thinking about doing is putting 2 microswitches on either side of the rudder servo so when i turn full rudder the servo clicks the switch and turns on the stern thruster motor.  There would be 2 switches - 1 either side of the rudder servo.  But is this actually possible?  i cant quite get my head round how this could complete a circuit?
Title: Re: Is this possible
Post by: barriew on January 08, 2009, 03:41:09 PM
Perfectly possible. This method was (is) used to provide simple forward/reverse control for the main drive motor without using an ESC. I'm pretty sure there is a circuit diagram on the Mayhem site.

Barrie
Title: Re: Is this possible
Post by: andrewh on January 08, 2009, 03:45:36 PM
Garabaldy,

Perfectly possible :}

First you might like to consider the wonders of FLJ's gadgets - some of which are intended to do EXACTLY what you describe.  You may well know this already - and indeed he does like a modest amount of cash for these wonders

So if you are going to do this - you can do exactly what you suggest - probably using microswitches
Assuming that the thruster is a normal DC motor what you need to do is to turn it on one way with say, full left rudder and t'other way with full right.  

The weapon of choice is  microswitches, and to reverse a motor you need basically two connected as a reversing crossover - I will find the circuit and post it if it would help.
You do not want the thruster running all the time so the switches need to be arranged to (as you say) function only at the ends of the servo travel.

As a say of simplicating the installation remember that you can drive the switches off a second servo plugged into a Y lead on the rudder servo - you can then do all your switchery on the slave servo, and mount it wherever seems convenient, and don't need to fit anything near the rudder or servo.

I will hatch a switch diagram.  I won't tell FLJ if you don't

andrew
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 03:49:41 PM
Yes, quite possible, it's how we used to enhance twin screw handling before electronic mixers arrived. In this case, one way to do it would be to buy 4 microswitches and mount them on top of each other in two in pairs, one each side of the rudder arm so that each pair is triggered simultaneously when the rudder is put hard over one way or the other. One of each pair carries the positive lead from the battery to the motor, the other the negative lead. Wire each pair the opposite way around and your thruster will run one way or the other depending on the rudder position. Put a fuse in each line of course.

Colin
Title: Re: Is this possible
Post by: Pepé Le Pew on January 08, 2009, 03:54:17 PM
Yes, quite possible, it's how we used to enhance twin screw handling before electronic mixers arrived. In this case, one way to do it would be to buy 4 microswitches and mount them on top of each other in two in pairs, one each side of the rudder arm so that each pair is triggered simultaneously when the rudder is put hard over one way or the other. One of each pair carries the positive lead from the battery to the motor, the other the negative lead. Wire each pair the opposite way around and your thruster will run one way or the other depending on the rudder position. Put a fuse in each line of course.

Colin
Do you mean this?
The  four diodes prolong the life of the two microswitches switches

S&y
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 04:08:14 PM
Not quite, S&y, mine was cruder, your's is more elegant and better.

Garabaldy, S&y's diagram  would be cheap, simple and effective! Just ensure that the microswitches can handle the motor current - shouldn't be a problem.

Colin
Title: Re: Is this possible
Post by: andrewh on January 08, 2009, 04:10:16 PM
 :-))What I said :-))

Neat and brilliant, Pepe - looks indistinguishable from a 2-way light circuit, too

Does this rotate your boat, Garabaldy?
I'm sure you know that screenwash pumps rotate both ways and act as modest bow (or stern) thrusters.  
No need to worry about the 12V rating, run them on 6V or 7.2 or whatever you have in the boat (but NOT the 6S6P lipo pack, please).  If the motor seems miserable it is often possible to replace it with something else more suitable (many car motors are 380 types - or derivatives of the same)
andrew
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 05:24:31 PM
"Not quite, S&y, mine was cruder, your's is more elegant and better."

You have to be kidding. Take another butcher's, follow the flow of current. Not one eeny-weeny electron will reach that motor since the wiring connections at one of the micro switches are iffy. Moderated...
Title: Re: Is this possible
Post by: Garabaldy on January 08, 2009, 05:53:32 PM
excellent!  Cheers guys!  The Y lead is exactly what im going to do.  That will make things much easier.  I did consider windscreen washer pumps but the boat will be quite big (1800 and with a hefty displacement i havent bothered to work out yet)

I may be getting ahead of myself with this as im still building the hull and im not sure if theres enough room in the stern for the thruster but if there is - i will be installing this lot.

Fair point about the load on the switches.  i will double check the rating the ones i bought have.

(watch this space on thrusters as i think im going to need advice as i am DIY all 3 of them.....)
Title: Re: Is this possible
Post by: Peter on January 08, 2009, 06:30:18 PM
Instead of the servo/microswitch setup, why not use a Y lead from the rudder channel, to an esc for the thruster?
The motor polarity can then be set to give the direction of movement required.
I have used this sytem for a bow thruster in friends boat, and it works fine.

Peter
Title: Re: Is this possible
Post by: Martin [Admin] on January 08, 2009, 06:37:57 PM
 
Quote
   Take another butcher's, follow the flow of current. Not one eeny-weeny electron will reach that motor since the wiring connections at one of the micro switches are iffy.   

Is the diagram wrong?
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 06:42:06 PM
Sure it's wrong. Just as wrong as wrong as you moderating my perfectly reasonable post, go figger.
Title: Re: Is this possible
Post by: malcolmfrary on January 08, 2009, 06:54:52 PM
Personally, I see nothing wrong with the circuit.  The microswitches are shown according to the convention that such things are "as in the box they came in", so the current through the motor will be zero until one of the mircoswitches operates at the end of the rudder throw, when the motor will run.  When the other operates at the end of the other throw, the motor runs the other way.
Switches would be better than an ESC because you dont usually want the thruster running with small rudder deflections, and with an ESC you would be stuck with just the deadband as a non-running time for the thruster.
Title: Re: Is this possible
Post by: catengineman on January 08, 2009, 07:02:34 PM
Hi Garabaldy,
I know this may be a tad late in the day to ask but you say you have not got a channel to operate the stern thruster.
Please let us know what channels you DO have
What you are operating with the above

the reason I ask is there are ways to switch between services so that *say channel 1 normal operation = port drive but when switched over will operate say stern thruster*

just a thought like

R,
Title: Re: Is this possible
Post by: Garabaldy on January 08, 2009, 07:13:49 PM
hi there i should have explained my channel usage from the start - sorry!

i have futaba 2.4gig 6 channel radio

the 4 proportional channels are taken up by rudders, throttle (coupled with a mixer) bow thruster, winch

the 2 on/off channels are for the fire monitors and possibly lights or a horn or some other on/off type function

G
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 07:15:26 PM
Look again. Check his normally-open/normally-closed connections.
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 07:17:30 PM
Looks OK to me, ignoring the diodes.
Title: Re: Is this possible
Post by: catengineman on January 08, 2009, 07:44:14 PM
hi there i should have explained my channel usage from the start - sorry!

i have futaba 2.4gig 6 channel radio

the 4 proportional channels are taken up by rudders, throttle (coupled with a mixer) bow thruster, winch

the 2 on/off channels are for the fire monitors and possibly lights or a horn or some other on/off type function

G

Thanks now this may sound a tad on the complicated side but it can be done,
The "fire monitor" switch /  controlled via a switch on the trany, then you can have a change over in the vessel which will swap out the current to other items
now if you use a six terminal double poll switch you can have say *fire monitors * in one switch position *stern thrust * in the other.
If you build a servo operated switch that has two six terminal double poll switches operated then you can have fire monitor and stern thrust or lights and ??? .
I an not that great with the tec side and have done just what I suggested in a boat so I know it works, sorry I have not got a picture and I could sit and draw a sort of diagram though the symbols would not be right and people of greater knowledge would know Im as thick as a plank of pine when it comes to this building stuff.

R
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 08:20:26 PM
You don't have to ignore the diodes. Just follow the pos/neg current direction - concentrate around the n.o/n.c  connections.
Title: Re: Is this possible
Post by: Garabaldy on January 08, 2009, 08:44:40 PM
hi there i should have explained my channel usage from the start - sorry!

i have futaba 2.4gig 6 channel radio

the 4 proportional channels are taken up by rudders, throttle (coupled with a mixer) bow thruster, winch

the 2 on/off channels are for the fire monitors and possibly lights or a horn or some other on/off type function

G

Thanks now this may sound a tad on the complicated side but it can be done,
The "fire monitor" switch /  controlled via a switch on the trany, then you can have a change over in the vessel which will swap out the current to other items
now if you use a six terminal double poll switch you can have say *fire monitors * in one switch position *stern thrust * in the other.
If you build a servo operated switch that has two six terminal double poll switches operated then you can have fire monitor and stern thrust or lights and ??? .
I an not that great with the tec side and have done just what I suggested in a boat so I know it works, sorry I have not got a picture and I could sit and draw a sort of diagram though the symbols would not be right and people of greater knowledge would know Im as thick as a plank of pine when it comes to this building stuff.

R

sounds interesting.  although i do not follow :embarrassed:  the problem i thought arrised here was because the on/off switch on the tranny can only set the servo to 2 positions.  with this servo operated switch surely that would mean if you harnessed it with 2 functions, there would always have to  be one function on.
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 08:45:39 PM
Well, the two triggering options look like this to me:
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 09:08:40 PM
That's it. Electrically, that is exactly how it should be. The only snag is that you should have written n.c where it say n.o on just one of your microswitches.
Compare your sketch to the one above.

NOW do you see why his wouldn't work?
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 09:13:30 PM
No, only one switch is triggered at a time so the other reverts to  the NC position. When the rudder is centralised both switches are NC so no current flows. Still can't see it PMK.
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 09:29:59 PM
Put it this way...
Refering to your (lower) sketch, look at the switch on the left-hand side of the motor. You have it that the motor is connected to the negative rail, via the normally-closed contact, right? All good so far.
Now look at the switch on the r/h side. It completes the circuit because the switch is closed, making contact to the positive rail, right again? But you made the mistake of writing n.o there.
In other words, the circuit would not be complete if the switch were open.

His circuit shows both poles of the motor connected to ground, hence why I said earlier that not one teeny electron would reach the motor.

Title: Re: Is this possible
Post by: craftysod on January 08, 2009, 09:32:05 PM
I think what pmk is saying top diagram shows both triggers  show nc wheras yours shows the correct way
You beat me to it, trying to be clever again
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 09:39:40 PM
The original diagram shows the "at rest" position (rudder central) with both switches in the NC position so that no current flows which is correct. My two sketches show the effects of the tiller arm switching each microswitch to close the NO contact at each side which alows the motor to run one way for one switch and the other way for the other one.

C'mon guys let's have some more input - one of us is barking up the wrong tree. or just barking....
Title: Re: Is this possible
Post by: craftysod on January 08, 2009, 09:48:00 PM
How about left side top no,bottom nc,right side top nc,bottom no
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 10:02:10 PM
Just assume that the wiring is initially as in the original diagram. Rudder amidships, no current flows. As soon as the tiller arm hits one of the microswitches it opens the currently closed contact and closes the other one allowing current to flow. Excuse messy diagram.
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 10:17:30 PM
"As soon as the tiller arm hits one of the microswitches it opens the currently closed contact and closes the other one..."

But if the tiller opens the currently closed contact, that means the circuit would be broken, which surely means no power would reach to the motor.
Does this sketch help any?..........



<edit>
1st sketch shows "N.O" twice on the L/H switch.
Apologies -- it should as shown in the lower sketch........
Title: Re: Is this possible
Post by: Colin Bishop on January 08, 2009, 10:32:24 PM
With your lower diagram the motor will be running all the time surely?
Title: Re: Is this possible
Post by: catengineman on January 08, 2009, 10:39:30 PM
sounds interesting.  although i do not follow   the problem i thought arrised here was because the on/off switch on the tranny can only set the servo to 2 positions.  with this servo operated switch surely that would mean if you harnessed it with 2 functions, there would always have to  be one function on.


Agree on that and my "multi switched unit worked as thus!  the rest and operated position of the servo is workable

 in position 1     Port motor esc controlled by Port stick then on other switch was stern winch esc controlled by L/R of Port stick
 in position 2     Bow thrust controlled by Port esc   then Forward Winch controlled by stern winch esc. and a link to both main motors would also switch.

The way I did it was in my mind logical in that when towing from the stern I would NOT require the bow thrust so that esc could be switched so I had independent use of the twin screws.
If I switched over the Port esc would give me prop control of the BT and along with that the other switches in the same action would link out both drive motors to one esc and give me control of the forward winch instead of the stern (cant tow at the same time from both)
I had one servo operating 4 switches at the same time the last switch in the unit changed light patterns on the mast.
It looked a right heath robbinson affair but it did work, I progressed to having a multi channel tranny now and have done away with the old system long ago. but it was just an experiment and it did work.
I will try to draw out and even remake the servo plate and switch position if you want to have a better look at what I managed to do with limited channels


R,
Title: Re: Is this possible
Post by: OMK on January 08, 2009, 11:18:30 PM
Quote
With your lower diagram the motor will be running all the time surely?

<Gulp!>

Oh, b****x!... I just realised!!
Yes, it will be running all the time. I mean, that was the whole point, wasn't it? Garabaldy wanted a motor he could reverse with the rudder, right?
Wrong.
I've just re-read his post.
Bummer - I got totally wrong.
Apology time.

So that's me eating dog poop for the rest of the week.

Ah well, someone out there might be grateful for the sketches, at least.
Title: Re: Is this possible
Post by: FullLeatherJacket on January 09, 2009, 10:25:41 AM
I've been watching........... ok2
The slickest solution is to use a P94 for both thrusters in Mode 2.
A cheapo solution - which doesn't even involve m*cr*sw*tch*s - might look like this:
(http://i167.photobucket.com/albums/u136/131251milbs/TwinThrusters.jpg)
Suit yourself.
FLJ
Title: Re: Is this possible
Post by: Colin Bishop on January 09, 2009, 10:37:34 AM
I've cancelled my appointment with the psychiatrist PMK.  :-)

FLJ, you are a cruel, cruel man....

Colin
Title: Re: Is this possible
Post by: tigertiger on January 09, 2009, 11:10:31 AM
Hi Dave

How easy would it be to get it to switch so both thrusters are thrusting port or both starboard, in addition to your fine solution above.
Title: Re: Is this possible
Post by: catengineman on January 09, 2009, 11:11:33 AM
I was about to ask the same question

 :-))

R,
Title: Re: Is this possible
Post by: FullLeatherJacket on January 09, 2009, 12:30:07 PM
If you want both thrusters to work in the same direction every time i.e. both squirt left when Port command is given - as opposed to Bow = Stbd and Stern = Port - then just reverse the two wires to one of the thrusters. If you wish to select between traverse (Spin) and slew (Sideways) modes while you're actually sailing, then check out this link:

http://www.action-electronics.co.uk/pdfs/P94.pdf 

Section on Mode 2 (Page 3) and Fig 8 (Page 7) refer. Wombat has this set-up in his Gry Maritha. He is such  a clever boy...........  8)

The cheap alternative to this  is to put a DPDT switch arrangement in the power feed to one of the thrusters (to reverse the polarity on command) and operate it using a spare ON/OFF channel, but as this would probably involve a s*rv* and m*cr*sw*tch*s I'll hear no more of it!

FLJ