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[Brian60]

I've gutted a micro servo so it is constant rotation. However it is too fast for the geartrain I want to operate ( the door its opening works at the speed of light instead of slowly)

Is there a better way of slowing it down then removing a battery/s (on 4 nicads 4.8v) from the power circuit? I can't change the gears as A they are 1 -1 ratio and all that is available in this size and B I've already after many hours got the thing totally assembled and bonded together

[C-3PO]

Arduino...

[TomHugill]

What radio are you using? If it's a programmable one you should be able to slow it easily. You can also use the turnigy servo slower to alter the speed it goes in both directions.

[Brian60]

Arduino...

How did I know that was coming I do have space on the arduino if necessary, as at the moment the only function for the uno is opening closing the stern doors, but its doing that via a motorshield and you can only operate two steppers with one motorshield, so I would have to look at adding what is basically just a tiny dc motor via a 'mash up' I could always add another motorshield -  I do have some more dc motors to add yet

I'll take a look at your option Tom, it sounds promising.

[John W E]

hi Brian

When you say you have 'gutted' the servo - do you mean that you have taken all of the electronics out and only left the motor drive and gearing.   If so, how about using a small variable voltage regulator circuit? I am sure Component Shop may sell one already made up - but - I do know there are a few circuit diagrams on the web and if you give me a min = I will see if I can find one for you

This circuit is easily made on a copper pin board - with about 3-4 components.

John

[Brian60]

well a washout with the Turnigy stuff, its only available from hobbykings australia warehouse and I am not paying the postage!!

I lowered the voltage by removing cells from the circuit. I got down to one 1.2v cell and it was still to quick, so hmmmm!

John I have four of the 317 voltage regulators. scratch that I have 3, burn't one out with too much heat from the soldering iron (don't ask  ) The circuit you have there is pretty generic so I'll give it a go and see if I can get the voltage down enough to slow it, but as c3po says I might as well get the arduino to do the work seeing as its already going to be part of the build. But I need something to do all the electrical test work with before committing to permanently attaching parts in the hull

[TomHugill]

well a washout with the Turnigy stuff, its only available from hobbykings australia warehouse and I am not paying the postage!!

I lowered the voltage by removing cells from the circuit. I got down to one 1.2v cell and it was still to quick, so hmmmm!

John I have four of the 317 voltage regulators. scratch that I have 3, burn't one out with too much heat from the soldering iron (don't ask  ) The circuit you have there is pretty generic so I'll give it a go and see if I can get the voltage down enough to slow it, but as c3po says I might as well get the arduino to do the work seeing as its already going to be part of the build. But I need something to do all the electrical test work with before committing to permanently attaching parts in the hull

I've got one somewhere Brian if i can find it you're welcome to it

[gra2]

Hi have a look at Dionysus Design they have what you are looking for.

Gra2

http://www.dionysusdesign.com/index.php - Admin

[John W E]

Hi ya Brian =- after a night of thought - by reducing the voltage, will the servo still have enough umph/power in it to operate the doors?  by dropping the voltage - you may also be reducing the torque on the motor so not giving it enough adequate power to move the doors.  Alternatively, you could increase  the amperage, but, then you run the risk of burning the motor out.    How about - possibly replacing the servo with a miniature one, but, not gutted and use something like a servo slower and expander from ACTion or Technobots.   Just me thoughts

John

[C-3PO]

Brian,

Arduino Pro Mini clone <£3-4 - size of 2 postage stamps

See BarrieW's excellent project for lifting the ramp at the back of his boat... http://rcarduino.freeforums.net/thread/186/first-arduino-project

Could use the same board  for several functions at the back of the boat and leave the Uno to do other things...

I presume you just want to flick a switch and the door goes up/down slowly( you could set the end points as well) - which would allow you to use an un-gutted servo

C-3PO

[malcolmfrary]

To control the speed of a small electric motor, what about a small ESC?  A quick goggle for "Chinese 10A ESC W/O brake" should find one.  The PWM output will be much more reliable than any voltage changing or current limiting can ever be.

[Brian60]

A couple of answers, first John, yes, even on just 1.2v the door opens easily but still too quick. Malcolm the idea of another esc is already worrisome, I have 4 on the thrusters and two for the main drives, it should be 5 for thrusters, but I have decided to leave that one out!

Jonathon I'm going to have a look at the arduino forum again, I must have missed that article! But as I said the operation at the moment is for testing purposes to get everything lined up before final attachment. A simple voltage reducer will suffice, before getting technical and allowing the arduino to do the work.

At the end of the day the door swinging upward and open is only the first part of a series of events. After that I have to work out an operating oilspill recovery head that will swing outward and drop a float into the water - I said it was a long and complicated build

[barriew]

Brian


If you use a 'whole' servo then an Arduino can control bot only the speed but also to extent of the opening - up to about 180 degrees in fact.


Barrie

[Brian60]

That's a problem Barrie, the servo which is basically just the dc motor and the gears - I've removed the rest so that it gives continuous rotation, is bonded to the module it will drive, my door is hinged to lift at the top, the opposite of your drop down ramp. I would have to undertake a lot of work to remove and replace it, see the images. My door is partially complete here, it now has the servo on the left hand end of the drive rod via bevel gears.

[John W E]

hi ya Brian

Do you still have the innards of the servo? (the electronics) that you have used to open/close the door.   Thought ..... the 2 wires from the drive motor of the doors reconnect to the servo board where the motor connections were made and use the electronic circuitry as a speed controller - adjusting the variable resistance pot to the correct speed of the door opening and closing - then with a bit of superglue lock down the variable resistor so it wont move - hey presto - doors slowed down and operating.     If you don't have the innards, I suppose you could strip down a redundant servo and add that ..... just another thought.

Think about these guys who do plastic magic and use servos to drive the models.

John

[Brian60]

Cheers John. Always the practical solutions to problems come too late

I ordered a couple of new servo's last night - another 2 weeks of delay waiting for the snail mail that is the spanish postal system to deliver. But I'll go through my rubbish bin and retrieve the 'innards' and see what I can cobble together for now. I cut away the module that is the motor drive last night thinking of no option but a new servo, so no harm in trying to reconnect the electronic bits to the old one.

[malcolmfrary]

Thought ..... the 2 wires from the drive motor of the doors reconnect to the servo board where the motor connections were made and use the electronic circuitry as a speed controller - adjusting the variable resistance pot to the correct speed of the door opening and closing - then with a bit of superglue lock down the variable resistor so it wont move - hey presto - doors slowed down and operating.     If you don't have the innards, I suppose you could strip down a redundant servo and add that ..... just another thought. Think about these guys who do plastic magic and use servos to drive the models.

When using the servo board as an ESC, I always used the transmitters trim slider as the speed control to make it proportional control rather than full on, maybe off.

Fixing the pot when using the servo board as a speed control only sets the center off when compared to the signal coming in to it.From that, it very rapidly transitions to full speed from a virtually zero deadband.  That's why I suggested the very small 10A ESC from China.  Nice big deadband, more gradual control, not much bigger than a standard servo board.  There are smaller ones, but they don't come with wiring attached so you need to solder your chosen wiring to them.
The alternative of a servo stretcher/rate tweaker should also be fine.  Either way, if it is part of a sequence being controlled by a single button press, it will need a source of signal to send it from open to closed, and, presumably, back again at the right time.
If not relying on eyesight to stop it in the right place, some sort of limit switch will be needed to either cut the servo motor supply or tell the control box to stop.