lightman281

Well.. Relativly unrealeated to RC however the servo idea entered into my head, so I'll ask.
I have a small metal box. About 6" long 4" wide by 6" deep. It has a hinged lid that opens the longway. It's made of thin metal, steel most likely.
I need to be able to open it via remote and stay open for a 30 or so seconds at a time. 120V is preferred. My inital thought was a high torque servo with a pushrod that would open the lid. However after looking at the cost of these servos it's a bit over for the estimated budget. Another thought was auto power lock actuators, however DC is not a preferred option as I'll be using 120V to power these units. I also belive that the DC actuators would burn out holding open the covers for an extended period of time.
Standard linear motors are WAY to expensive for one. Much less the 9 boxes I need to open.
Pneumatic was a thought as we have an air compressor already, however It seems a bit pain in the behind making all those hoses.
The application is having a box with pyrotechnics installed in it. Open the lid, fire the pyro and close the lid. These boxes are installed flush with the stage and are strong enough to support the weight of our performers. They could be spring loaded to close after power is removed. Any motor system does not have to be installed in the box but can be installed with a push rod system. We have 120V AC readily available and I prefer to control them with an on/off AC line.
I need an idea and somewhere I can buy them. Any engineers on here?
Your thoughts?
Thanks. I'll have pictures when I'm done.
Wade

Lynx

Need more information than that. How much does the lid weigh, and what exactly is your budget? BTW, unless you're going to be using pneumatics you're probably going to have to use DC. Most of the stuff like what you're talking about that runs on AC is all for industrial use and you don't even want to look at the prices

lightman281

I would guestimate the lid weighs about 1/4lb... I don't know exactly as I didn't build the box.. Just ordered it. I cannot remove it to weigh it. But I most likely don't have a scale that will weigh such a lightweight thing.

If DC is an only option I'll just order a bunch of door lock actuators and replace them when/if they burn out. However I'm concerned that my power supply will have to be so large to accomodate the inital shock of opening all nine simulataniously that it will be too expensive.

My guestimated budjet is less than $200. My producer/boss doesn't give me any budget to work with but he bites on something he likes. He loves this idea but if it costs $500 he won't go for it.

Lynx

Why by a power supply? Take the battery out of your car and use that =O 0 cost. (Just make sure you have a buddy with a car and jumper cables in case you kill it) An automotive battery is designed to handle high current hits, kind of like the several hundred amps starting it can take. You'll definitly HAVE to find out the electrical charactoristics though, door actuators are designed for quick hits. Don't they usually lock in one position untill the current is reversed to pull it back? I know this is how they work in a car, but I don't know if the mechancis are extra in a car or part of the actuator itself.

lightman281

Well the down side of using a battery, is the type of install.. This is a permanant install and will be used many times a day, both for performance and preset/loading. I have already considered the idea of a car battery with a trickle charger stowed away. However I'm concerned about overcharging and the possibly explosive vapors lingering under our stage.

As for positioning, I suppose I could neutrally load them with a spring so I could push open, release, pull close, release. Hmmm.. Thougts thoughts thoughts..
Perhaps they will have enough tension within the solenoid mech to hold the lid open by itself...

I suppose I could control 2 12V relays with my 120V relays.. One to open, one to close.. Use a 120V coil with a contact rating for 12V DC about 10amps for all nine?

Hmm..
Wade

Lynx

I don't think that'll do it. I looked up power lock actuators and found them all over the place. Couldn't find any hard electrical specs on them though so I can't tell you what the current draw will end up being. But I can tell you 10amps would only be enough for 1. The wiring harness's they're selling for the door lock kits are 30 amp kits. So the impulse current those things draw is HUGE. Most any other way I can think of involves servo's and that's too expensive, the servo's alone are expensive but then you'd have to find a way to drive them. Pneumatics are probably best. Reliability with pneumatics is much much higher as well.

lightman281

I agree they do draw quite a bit of juice, however they can't be THAT much.. I'm running my aftermarket door lock and power windows on a 20amp fuse in my truck. They all operate simulationusly and won't blow it.. But again, if I'm using 9 of these at once it' would be quite a spike. 40-50 amps perhaps? I'll see what I can find on the specs for those motors.
If they do turn out to not be a viable option where could I go to purchase pneumatic gear? And how expensive are they?

Thanks for the good conversation, keep it coming. I enjoy the geek factor
Wade

strato911

Although this is not my area of expertise, here's a quick thought:

Since this is a permanent install, and there are explosive fumes present, I would recommend using pneumatic gear:

- It may take more work to install, but that's a one time thing.
- It makes it safer, since the electronics are moved away from the explosive fumes.
- Lynx already mentioned the higher reliability.

Dylwad

My Feedback: (11)

http://www.allelectronics.com/cgi-bin/category.cgi source for cheap pneumatic cylinders, as for the plumbing, you could use a 1/8 inch or 1/4 inch plastic line, and you can find press lock fittings that make install a snap. as for valves, you could do ball valves from home depot, just be sure to use a filter/regulator in the line before any valving, if you wanted to get fancy with the valves, Graingers supply carries a wide variety of solenoid valves for commercial air conditioning, you could set it up on a 3 way switch, center is off, up is open, down is closed, just make sure you have push-pull cylinders, the cool thing about using a solinoid valve for each box would be you could wire it in to the lighting control panel, making it almost automated, as for under 500 bucks...........might want to go with the ball valves, and at 60-90 psi these little cylinders pack a punch

Dylan