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DT robotics, major design project
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dyrodium
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DT robotics, major design project

Well, as anyone who has recently gone through, or is about to or doing, in design technology yr 12 you are required to do a major design project, a project completley of your own choice... and a tonne of documentation Laughing

Anyway, I start yr 12 term four and so start my design project then, but i want to get a nice head start on it, so i'm doing a fair amount of research to see if my idea will work, but i'm not prepared to give it out *yet* as it's so insanely different if it works it'll be awsome... yes it is a robot Laughing Probably not a combat robot though!

A few questions;
SOLENOIDS:
Where can you get big, powerful solenoids? I'm searching the net, but so far the best solonoid's i've ever seen have come from an ancient U-matic video player I picked up, awsome chunks of engineering those things! However for the project i'll need about 20 preferably new ones.

Also, when you activate a solenoid, the electromagnetic field pulls the ferrous rod IN to the solonoid. I need a force that moves OUTWARD when the current is applied... I was thinking of possibly positioning the solenoid facing in, and on the other end fitting a non ferrous end, so that the IN force is then used as an OUT force... would that be possible?

Hmm, looks like I may even need to custom make my own solenoids, would that be too hard? (there is a fair amount of budget going into this, I wanna do real well in DT Very Happy )

CONTROL:
What kind of sensor picks up a rotation on all three dimensions? I was thinking a 3D gyro or possibly two/three rotation sensors (like in the snoil device), and again where can I source them.

Another aspect needed will be the completly custom control system, decoding the recievers PWM into the movement of the solenoids, which chip should form the base of this module? I've heard that picaxes might not be up for the job, but I don't know of any other chips that would be suitable. I'm assuming as only a full on or full off control is needed the system should be reasonably simple compared to a PWM motor control.

PROGRAMING:
I've also noticed that the picaxe code seems to be in an unstructured format (true?), would that make the likely complex code be insanely hard to debug and all together work out?

A few other notes:
>I plan to use the spectrum 6ch for control.
>I'm aiming for a fairly small finished robot, so I may use a small NIMH battery pack or a lipoly battery.

Thanks in advance, this will be a huge undertaking Shocked I can do it though! (I hope Laughing )

EDIT: it's solEnoid lol
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Post Fri May 05, 2006 12:02 pm 
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Daniel
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Any use to you?

http://www.surpluscenter.com/sort.asp?UID=2006050421101238&catname=electric&keyword=ERSO

Post Fri May 05, 2006 12:13 pm 
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dyrodium
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Hmm interesting, seems most of them run on too high a voltage though, 24v or 115AC. That 12v one looks pretty good though, forgot about surplus center! Still, the problem is they all pull in, i'm not sure how you could modify them to push out, as most have an enclosed back. I'll have to do some experiments with some solonoids this weekend to see if a pull can be converted into a usefull push action. Smile
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Post Fri May 05, 2006 12:20 pm 
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Philip
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Starter motor solenoids pull in but use a leaver to push the gear. Could you fit a leaver to reverse the direction of movement?
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Post Fri May 05, 2006 12:44 pm 
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Totaly_Recycled
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solonoides will only pull in it doesnt mater the direction of curent flow they even work with a/c
What you need to make is a lineal actuator if you want push and pull .They can be made to function similar to a brushles motor type solonoide configuration but they would need a lot of electroncs like hall sensors etc so the controler would know when to step and what direction to step and send imformation back to the chip when the actuator is at the end of the stroke etc . iff you want push pul with solonoides you wil need to use one for each direction .

Post Fri May 05, 2006 1:24 pm 
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dyrodium
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I only need a push motion, a spring return like on standard solenoids would be fine. Yeah I considered that but as you can see, the complexity kind of makes it useless. I may use the lever suggestion or see if the mod to the solenoid can be done (still pulls in but in the process pushes out of the other end a plastic/aluminium spike).
Basicaly the solenoid is a direct interface in it's movement, it doesn't connect to anything else like legs or such. Smile
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Post Fri May 05, 2006 1:39 pm 
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Totaly_Recycled
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Just anohter note as ive been researching this on the net for one of my own projects and doing experiments .

If you wish to build your own you could make a double acting type -- ie a coil on either end, the ferous core in the center and a non ferous rod as the push-pull rod .So if you activate one coil it will pull one direction.Turn that one off and energise the other coil it will go the other way .
Solonoides work best if they start with the iron core a fair way inside the coil to start with.
For real strong pulls at least1/3 to 1/2 way into the coil is best starting point . So if you want to make a long stroke you will need a long coil and a long plunger so that the desiderd stroke length is basicly half the plunger and coil length .This starts makeing them heavy and cumbersome and power hungry .

Post Fri May 05, 2006 1:43 pm 
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dyrodium
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Heh as with all things eh, the classic three way triangle, choose two Smile
I'm basicaly after a short lived, powerful *pop* of energy, no more than 5cm in length, i'm sure 3cm would be fine. I ruled out hydrolics and pneumatics early on due to the cost and lack of knowledge in them, and thought solenoids would be best. I'll do some experimenting to decide which way to go. Sooo glad i'm getting this started now Laughing !
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Post Fri May 05, 2006 1:49 pm 
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Totaly_Recycled
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what length of stroke and how much do you require the solonoide to lift mabee i can poit you towards different types that might be suiatable .vertex uses two small ones .and one larger type .one trigers the throttle on the i/c motor one closes a valve for the selfrighter .and the bige one which is a modified ford starter solonoide will lift the back of the robot off the floor

Post Fri May 05, 2006 1:51 pm 
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Totaly_Recycled
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ok the starter solonoide if the iron core is 5mm inside the coil and its been modified so both the pull in and hold in coils are paraleled ..on 24 volts it will travel 25 mm stroke and lift aproximatly 60 kgs
..fairly quickly

Post Fri May 05, 2006 1:54 pm 
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dyrodium
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Whoa... that's perfect Very Happy
It would only need to move max 20kg... but w00t more powa! How much are they?
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Post Fri May 05, 2006 2:42 pm 
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Knight



Joined: 30 Mar 2006
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PICaxe code is by no means complex, i'm using a PIC for my software major project at the moment and plan to use several in my bot as it progresses.

I can help you there if you want, as if i remember rightly you are allowed in DT to comission others to do the work, you just have to design it.

And no its not unstructured, it is a derivitive of BASIC (alright so basic isn't the most structured language out there...but that isn't the point)

Post Fri May 05, 2006 4:08 pm 
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prong
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hmmm, so you need 20kg of push?

otherwise car door actuators are cheap, but they only do about 3kg, push and pull.

also remeber that any of these big solenoids will draw a fair amount of current

Post Fri May 05, 2006 5:50 pm 
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Totaly_Recycled
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the one i used pulls about 12-15 amps on 12 volts never measured it on 24 it could lift around 18 kgs on 12 volts once they have done the lift they can hold a lot more at their closed position .i cant rember the weightof it but i would guese around 500 to 700 grms each they have a lot of copper and steel in them .

Post Fri May 05, 2006 6:57 pm 
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dyrodium
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Nice, yeah car door acuators would need some sensor to tell what position they are at, solenoids are given. And the push wouldn't even need to be that huge, it's just nudging something along the ground, not raising it clear off. Smile
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Post Fri May 05, 2006 7:39 pm 
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