Anyone into Radio Controlled things?

chillidoggy

Specifically servo motors. I want to know if I can get a 12v (or less) one and graft it on in order to open and close a heating air butterfly valve in my car. Needs to open and close 90 degrees, either open or shut.

bertie

wives ?

ROOG

RC servos are neat, really small, quite powerful, nowadays they are relatively cheap and readily available and as far as I know most of em can do 90 deg rotation or more. 

However, they nearly all run off 4.8 to 6.0 Volts. The older analogue ones, (still available) use a pulse width modulation signal to control their position. If you put just power on them they sit still, you need a variable width pulse to move them, typically 1ms to 2 ms from one extreme of motion to the other. Digital ones require a different control signal, but similar principles apply, just need digital compatible controller.

There are 12V servos, but these tend to be quite specialist, more expensive, robust and bigger.

Not sure how much torque your butterfly valve needs to move it but most manufacturers quote torque outputs for each model of servo, some are seriously powerful.

You could get an analogue servo, buy a servo tester, (quite low cost) and build/buy a 12V to 5V DC regulator to power the thing. The tester has a knob on it to allow you to manually move and position the servo, so if you put it to mid position the servo moves to its mid position.

Quite a bit of effort, but I cant think of a more readily available bunch of parts to do the job particularly if you want the proportional position control. I did see a 12V heating control valve but that would have needed much modification too.  

ROOG

For a Servo tester, I was thinking of this sort of thing,

http://www.amazon.co.uk/Servos-Checker-RCECHO-Version-Edition/dp/B00ETTUFI0/ref=sr_1_9?ie=UTF8&qid=1384872769&sr=8-9&keywords=servo+tester

An example of a 12V to 5V converter

http://www.amazon.co.uk/Car-Power-Converter-Display-Supply/dp/B008VORADW/ref=sr_1_1?ie=UTF8&qid=1384872825&sr=8-1&keywords=12v+to+5v+converter

Or if you don’t mind using the cigarette lighter socket you could consider this;

 http://www.ebay.co.uk/itm/Storage-Options-54585-Scroll-Excel-7-Android-Tablet-5V-In-Car-Charger-Adapter-/151161340238?_trksid=p2054897.l4275

Ianpdq

Have a look here you mite find something  http://www.mindsetsonline.co.uk/Site/Home

ROOG

Ianpdq said:

Have a look here you mite find something  http://www.mindsetsonline.co.uk/Site/Home

I love stuff like that, I used to get my girls soldering maplin kits at Christmas, mini LED christmas trees, digital dice, little robot bug things.

I don't think they have ever forgiven me!

>:D<

Misterg

You can buy a servo, rip the electronics out of it and connect directly to the motor. You can then drive it through ~100degrees by applying ~5V to the wires (either + or -). I wouldn't try it with 12V, though.

chillidoggy

So from this I'm getting that if I want to use a complete servo, then I can't just stick + or - 5v DC through it, unless I give it a variable width pulse supply, but if I take out the controller I can?

 

How does the motor know when it's got to the right position if the controller is removed?

And also if voltage is removed, presumably the motor stops, they don't spring back or anything?

 

EDIT: Ooooooh I've just had a look at the mindsetsonline site! I've seen an actuator that might be what the doctor ordered, but I'll have a much better look when I get to work!

ROOG

Depends on whether you want to know where the servo is? If you take the guts out as Misterg says and run it as a motor with a gear box, putting 5V on it will make it go until you take the power off, revering the polarity will make it go the other way until you take the power off.

Most servos have inbuilt mechanical stops, if you keep hitting them you might strip the gears. The electronics is designed to stop this happening and the servo tester has a knob on it to allow you to select the position proportional to the position of the knob, I don't know if you need this control or whether you just need to 'wang' it from one extreme to the other?

If you take the power off it is unlikely that it will 'spring back' there is a massive gear ratio in the gear box, they tend to stay put with power off. 

 

chillidoggy

I want to control either one of these vents (I have a pair of the first ones anyway) in the car footwells, hence the 90 degree movement. As I see it, power on to open, microswitch shuts off motor. Reverse polarity, motor operates in the other direction, stopped by microswitch. Haven't worked out how to what type of switch I would need to reverse polarity though, maybe DPDT. 

 

http://www.mindsetsonline.co.uk/Catalogue/ProductDetail/linear-actuator?productID=78dacc9a-bbf8-4762-913c-72a4d1ca2729&catalogueLevelItemID=cc7532f6-22eb-4a9c-9e57-8c3ec18bbb31

http://www.carbuildersolutions.com/uk/demist-y-splitter-vent-with-butterfly

http://www.carbuildersolutions.com/uk/y-splitter-vent-with-butterfly-3-x-60mm-outlets

FX_Munkee

Why not just a "bog standard" geared DC motor?
comme ca
I've used stuff like that before for similar mechatronic projects, the gearboxes normally have a slip clutch in to prevent damage from hitting the stops as well.

chillidoggy

Looks interesting, no fannying around with volt dropping, but I wonder if it's likely to destroy the the plastic valve spindle with the torque, though? The previous acutator (3-6v dc motor) had adjustable microswitches to cut the power, otherwise it'd have to be on a timer. Found a volt dropper - http://www.amazon.co.uk/Car-Power-Converter-Display-Supply/dp/B008VORADW

ROOG

 Thinking along the lines of keeping it simple how about a Bowden cable with a knob on the end? something like a speedo cable?

chillidoggy

Simple? Good grief, I'm Emp's right-hand man when it comes to over-complicating simple things!

Seriously, I have looked at that too,and it may also be a possibility. I have a pair of solid wired bonnet release pulls, but they'll never go around the curves required. I'm thinking a flexible cable might be better, so that's another option too.

Misterg

There's a simple circuit with a DPDT switch and a couple of micro-switches to limit travel that would work with either the servos or that geared motor.- something like this:

http://i.imgur.com/FKJlfzX.png

(but with a DPDT switch instead of the relay).

A car USB power adaptor would be a handy source of low voltage for a servo.

chillidoggy

See where you're coming from there. I looked at the actuator from mindsetonline again, and thought the plastic block should be made from metal, I can do that, but as they've no idea of torque, it's impossible to make an assessment of how much force it's going to provide. The geared motor is certainly an option, but whatever I do, it will need to be powered off when it reached either open or closed position. The idea is for the occupant to flick a switch on the dash up or down to open/close the butterfly.

More detailed prevarication is required at the weekend, methinks, but I reckon the solution is in here somewhere.

 

Thank you for the assistance, chaps.

Ianpdq

Would this work http://www.ebay.co.uk/bhp/12v-pull-solenoid or http://www.ebay.co.uk/sch/i.html?_trksid=p2050601.m570.l1311.R1.TR10.TRC0.A0.Xactuator&_nkw=linear+actuator&_sacat=0&_from=R40

chillidoggy

Not really. The solenoid will spring back unless it's powered up, and I don't want to leave it powered.

Ianpdq

What about the  Actuators

FX_Munkee

Stepper motor? They're surprisingly cheap nowadays but, as always, control is the real issue.
Hydraulic/Cable? That would give you exact range with no feedback req.

Anyway re: the geared DC motor, I never did the electronicy bits for designs but isn't there a basic switch circuit based on current draw? I'm thinking electric windows here. ie motor meets stop, draws more current, sensed, relay de-energised, all within a few ms?

Engineering is so much more fun when it's somebody elses problem...

chillidoggy

Ianpdq said:

What about the  Actuators

No, they're way too big, unfortunately.