Minature actuators/ servos?

[Merlin66]

I have an application where I have to rotate a shutter (on a 3mm spindle) by almost 90 degrees and then switch on a 12V supply to a lamp.

I was thinking of a small 12V servo (a la RC stuff) and a limit switch to switch the power on and off the lamp.

Do I need any sophisticated drivers??? Yes, ideally if it could be controlled through a USB port so much the better.

What do you think/ recommend??

[FraserClarke]

I've used the phidget stuff for this before. It's about £40 for a servo driver card with a USB interface. There are probably cheaper alternatives (arduino?), but the phidget interface is very well documented and has always worked for me.

[Merlin66]

Thanks for that!

You may have already guessed - this is to control the positioning and illumination of the reference Neon lamp in front of the spectroscope slit.....

Robin L. has done similar with a "Motor Bee" card which also switches the power....

ROBIN'S ASTRONOMY PAGE Spectroscopy_9 - LHIRES remote neon control

What other options?

[theodore]

Sounds like a job for Arduino - or cheaper Seeeduino, you can step the drive low power motors directly from it too. Look up the code and examples at arduino.cc

theo

[Photosbykev]

I'd go for the Arduino, plenty of I/O, built in PWM stepper control and easy to programme as there are thousands of open source programmes and advice available from the Arduino forum. You can also buy a precut case to house the arduino to tidy things up

[Merlin66]

Whoooo

I looked at the Arduino website...it has something I'm sure, for everyone.... but I didn't even understand the basics to be able to figure out what I may need/ want....totally lost.....

[pete_l]

Sounds like a job for Arduino - or cheaper Seeeduino, you can step the drive low power motors directly from it too. Look up the code and examples at arduino.cc

theo

Or if you really want to get down and dirty with PICs for very little money, there's always one of these for a fiver - though the P&P rather kills it if you only buy one.

[Photosbykev]

Or if you really want to get down and dirty with PICs for very little money, there's always one of these for a fiver - though the P&P rather kills it if you only buy one.

#

I like the idea of the ChipKit Max32 Arduino, it really does turbocharge the arduino concept

[Merlin66]

Sounds exciting, but please be gentle with me.... I just want to move a shaft 90 degrees and switch a 12V supply....usb to serial with pic options - don't understand!!!! Sorry:(

[pete_l]

Sounds exciting, but please be gentle with me.... I just want to move a shaft 90 degrees and switch a 12V supply....usb to serial with pic options - don't understand!!!! Sorry:(

Meccano? One extreme to the other

[Photosbykev]

ok back down to earth. What about a ready made servo tester to drive the servo? or do you want some automation? maybe the Pololu range http://www.hobbytronics.co.uk/pololu-servo-controller-6

edit: you could control the lamp using another RC switch on one of the spare channels of the Pololu board.

[themos]

You mean like this Lego train that was actually used to move a lamp in a research telescope?

:-)

[Merlin66]

I'm beginning to like the Lego solution more and more....

Guys,

you've got to understand I just want to do a job...not start a new career...

""The channels can be configured as servo outputs for use with radio control (RC) servos or electronic speed controls (ESCs), as digital outputs, or as analog inputs. The extremely precise, high-resolution servo pulses have a jitter of less than 200 ns, making these servo controllers well suited for high-performance applications such as robotics and animatronics, and built-in speed and acceleration control for each channel make it easy to achieve smooth, seamless movements without requiring the control source to constantly compute and stream intermediate position updates to the Micro Maestro""

I recognise some of the words... but don't see how to move a shaft 90 degrees and switch on a lamp....sorry...

[Psychobilly]

90 degree rotary solenoid a cam and a microswitch? - We used to use this approach for intra cavity shutters on lasers...

Ledex Products - TESTCO

[Photosbykev]

I'm beginning to like the Lego solution more and more....

Guys,

you've got to understand I just want to do a job...not start a new career...

""The channels can be configured as servo outputs for use with radio control (RC) servos or electronic speed controls (ESCs), as digital outputs, or as analog inputs. The extremely precise, high-resolution servo pulses have a jitter of less than 200 ns, making these servo controllers well suited for high-performance applications such as robotics and animatronics, and built-in speed and acceleration control for each channel make it easy to achieve smooth, seamless movements without requiring the control source to constantly compute and stream intermediate position updates to the Micro Maestro""

I recognise some of the words... but don't see how to move a shaft 90 degrees and switch on a lamp....sorry...

forget all that, it's just standard RC bull that means the servo movement is nice and smooth

on the other hand this line

"A free configuration and control program is available for Windows and Linux, making it simple to configure and test the device over USB, create sequences of servo movements for animatronics or walking robots, and write, step through, and run scripts stored in the servo controller."

Means you get a windows programme to control the servos over USB i.e. how far they move and how fast and when to turn the switch on/off.

At £15 it's a bargain and it will work with very little effort or knowledge

and there's more

it has a RS232 interface so commands can be sent serially so there is the potential to use an ASCOM driver (just thinking out loud about astro applications)

[Merlin66]

Kev,

Thanks for that.

I've gone with the Pololu board plus a relay and a small servo motor.

Keep you posted........

[Merlin66]

Well, HobbyTronics delivered the Maestro 6 channel controller and the other bits within a couple of days - great service!

The key to my (limited) understanding was to find the Download of the Pololu Maestro Command Centre program and the associated .pdf file.

I've already managed to install the controller onto my XP machine, and can see now what is required to send control signals to the small servo and switch the relay....in fact I can see how it could also be used to control the S-W focus motor..."one screen does all"

Thanks for the hand holding - more the fear of the unknown than it's turning out to be.

I'll update when I get a 12V connection for the servos....so far so good.

Onwards and Upwards.

[themos]

Once you've mastered controlling the servos from a C# program, you will be on your way to writing an ASCOM driver for your device!

[Merlin66]

Hmmmm

It's sometimes amazing what can go wrong...go wrong....go wrong.....

I installed the PoloLu Maestro drivers and played with the controller...great fun!

BUT

I had to install an update to my AstroPlanner on the same PC....crash and burn!!

I tried everything...three hours later....still no success...

Slept on it overnight...then decided to restore settings (XPsp3 machine) to earlier in the week ( before the Pololu installation) - well, well, well it installed (with errors associated with polling serial connections...)

I haven't built up the courage to re-install the Pololu software!!

Any ideas on how to ensure there's no conflicts when I do????

[Trull]

Hey how about some meccano and a length of cord?

Failing that I use Arduino + a Ladyada motor shield for servo control.

[Merlin66]

The POLOLU Maestro seems to be able to control the servo OK...just need to get a 12V 2A relay to come together......