need circuit help for a pressure pad-motorised door project.

[rancid rock]

hey,

i need a circuit similar or the same as the following:

needs two pressure pads preferably (one on each side of the door)
And a door that opens when the pressure pad is pushed down, then stays open for a timed 10 seconds and then finally closes again unless the pressure pad is pushed which would reset the timer

if u know how to, or have a circuit like this or similar coud u plz post here, because i can always make modifications to both the project or circuit.

I will be using a microcontroler PICAXE 18.

Also any advice or comments are welcome

thankyou,

 

[philba]

this is pretty simple. there are security sensor foot pads. You should be able to interface them to the micro easily. I don't think they are super cheap though. You could make your own but the security ones will probably last a lot longer. conductive foam between two conductive sheets will have resistance that is inversely proportional to the pressure on it.

I assume you have the motorized door and know how to control it. if not, you'll need to post actual details.

when your micro sees the foot pad sensor go on, activate the door, wait 10 seconds and then close the door.

you should consider a safety interlock that prevents the door from closing on some one or some thing. probably a couple of IR beams.

 

[philba]

ok, now I'm confused. I see an almost identical request about 3 posts earlier. Is this a class project? much to similar to be coincidence. do some work first...

 

[rancid rock]

yeh thanks heaps philba, but i also need to know about motor reversal and how to power my door to open

help needed plz

thx

 

[philba]

yeh thanks heaps philba, but i also need to know about motor reversal and how to power my door to open

help needed plz

thx

ok, now I'm confused. I see an almost identical request about 3 posts earlier. Is this a class project?

well? you're going to have to put out some effort since this is a class project. a little honesty here would go a long way.

 

[rancid rock]

this isnt a school project!!!!!!

joshthesim user is also me......i didnt mean to post this on that account!!!!

so can u help now man?

 

[rancid rock]

if ur wondering as to why i am wanting to do this project,

it is because im not good at electronics etc. yet and want to get better.
iv'e been wanting to do this project for a long time as there is woodwork involved

okay?

why do i feel i need to justify myself to get some experts help

 

[philba]

ok, what do you have already? pads? motor? mechanical assembly?

what is your budget?

do you want to build it all from scratch or assemble premade components?

 

[rancid rock]

budget bout $80-120, and i dont have anything except for the PICAXE 18, im making the circuits on circuit boards, which i get for free so only cost is the components

help plz mate

 

[philba]

OK, your first order of business is to figure out how strong a motor you will need to open and close the door. I guess you will need the door, too. I'd look for a DC motor. You can test it out without any circuitry - just apply voltage one way to open, reverse the terminals to close.

Once you know the motor, then you can do the motor controller. There is a recent thread on relay based bidirectional control of DC motors. You will also need to build the power supply. You could use an HBridge but I'm not sure how cost effective it would be compared to a relay (which is pretty cheap).

next, you will need 2 limit sensors. one for open and one for closed so you know when to stop the motor. You can use microswitches, hall effect devices or opto interruptors. I'd probably use optos. These are devices with an LED and phototransistor with a slot between them. Insert an opaque object in the slot and the PT stops conducting. very easy to interface to your picaxe. when you get to this point, ask... I'd get that working next.

Finally, get the pressure pads working. Not sure how this works but I suspect it's based either on switch closure or resitance decrease. in either case it's pretty easy to interface to a PIC. By the way, the conductive foam that ICs get shipped with might work for this. I just did a little test and the piece I had went for 8K ohms uncompressed to around 1.8K compressed. put it between two metal plates and you can use the resistance to determine if there is pressure on the pad. I don't know if it will last very long, though.

I would also build in some sort of safety interlock that will reverses or stops the door if something gets in the way while it's closing.

On your picaxe, you will need at least 5 inputs and 2 outputs.

 

[rancid rock]

thx heaps,

that should be cool, cause the PICAXE 18, can have up to 8 outputs and 5 inputs.

and it would be preferable if it would run off 5v DC.....is this possible?....

and i dont exactly need a full on pressure pad...cause they r a rip off, my pressure pad will mainly be like a push switch......or someone suggested keypad...hmmm

 

[philba]

you can run everything off of 5V. however, you will have trouble finding a motor strong enough running at 5V. I would suspect something in the 24V range but who knows. Take a look at garage door openers. that may be overkill, though. I don't know what's available in oz but if there are surplus mail order places, I'd start there.

also, the door speed will be a factor. If you gear down, you can use a smaller motor but the door will open slower.

 

[rancid rock]

it dosent matter if the door takes 1 whole minute to open, hehe that woud b funny.

but anyway door speed isnt a constraint for me, also the door will be very light and im still deciding on how im going to have it open.....like on top rollers or something......

 

[philba]

yeh, you've got to get that and your drive mechanism figured out first. I think you have 2 choices: chain driver or screw drive. I'd probably do a screw drive by using a standard threaded rod.

I'm pretty sure you would want faster than 1 minute. I'd guess 10-15 seconds max. With a threaded rod, you can fugue out how fast you have to turn to meet your target time.

 

[rancid rock]

i have now figured my way of opening the door.....using a nut and bolt sorta principle, very slow yes, but i'm not wanting to work with pully's and it will do fine.

 

[Boncuk]

need circuit help for a pressure pad-motorized door project

Hi Kirby,

as I understand you are looking for something triggering the MCU - and it should be done using pressure.

Here is a simple but reliable solution for it: Use a pressure switch which you can salvage from a junk laundry washer. If you are lucky you will obtain a switch with adjustable trigger pressure. Connect the pressure port to the cusion you will be using. The switch will close and activate the door opener via the MCU.

My home (under construction) will have sliding doors operated by pneumatic cylinders and activated by I-Buttons. The pressure on the cylinder makes it more difficult or even impossible for burglars to push the door open. A pressure of 30psi on a 2inch dia piston is hard to move.

(I must install that because Thailand is full of burglars.)

Hans