I was asked at work to come up with a drawer cycle testing idea , I decided to use a higher speed linear actuator. I understand that I will need something to tell the actuator what to do, like an arduino. other than that I'm not too sure on what other electronics I will need. has any one seen anything like this or can someone give me guidance on this project?
Can you explain the "drawer"? I'm not a native English speaker, don't have an idea what that might be.
What type of linear actuator do you have in mind (moving coil, gear rod...)? Link to the product page?
Limit switches on each end of travel to tell the controller when to reverse direction. Could be mechanical or optical sensors. An Arduino Uno, in my opinion, is the easiest to start learning with. Once the actuator is chosen you will need some sort of driver for it as an Arduino can only supply about 20mA (safely) on any output. What is the stroke length required? How fast must it cycle, cycles per second, minute?
the drawer pulls out about 12" so that should be the stroke, not sure how fast it needs to happen, should just be the normal speed some one pulls a drawer out.
What is the mass that needs to be moved? I mean the weight of the drawer and its contents. My guesstimate for normal speed of opening is about 1 foot per second. Sound right? For the actuator, there are several options. Screw drive linear actuators are probably not fast enough. pneumatic and hydraulic cylinders are probably fast enough but require a pressure source and valving. Maybe a gear motor with a rack and pinion would fast enough and be the easiest to control (H-bridge, limit switches and optional encoder).
yes, that speed sounds about right not sure what the drawer is rated for but it cant be more than 10 Lbs i would think, also i found a few high speed electric linear actuator and it seemed pretty fast. https://www.amazon.com/Progressive-Automations-PA-15-24-11-Linear-Actuator/dp/B006P58U7O/ref=pd_sim_sbs_328_8?ie=UTF8&dpID=31CjHYGjlqL&dpSrc=sims&preST=_AC_UL160_SR160%2C160_&refRID=FAHVG2HKGW8XN3SW2AYR
although i think that this is pretty bare bones, no limit switches i think.
From what I can see in the link provided, there are no limit switches. Limit switches can be added easily. One thing troubles me about the linked actuator. On the manufacturers page linear-actuator the duty cycle is specified at 20%. To me, that means that it should not be continuously stroked (especially at full rated speed and load). More like, stroke for 1 second and rest for 5 seconds. Perhaps you could consult the manufacturer to confirm the suitability of that actuator for your project. At some point you will need to list all of your requirements in specific terms. Force required, stroke speed, stroke frequency and stroke length at a minimum will need to be specified. You will need that information before you talk to the manufacturer.
If you go with that actuator you will, I believe, need an h-bridge capable of handling a minimum of 10 Amps and a power supply of similar capacity. Limit switches can be mechanical, hall effect (magnetic) or optical.
i realized the duty cycle just now, seems pretty common for these to have a cycle like that. so with correct programming we should be able to keep that 20% in check. other than that what else should i think about
I notice, on the data sheet on page 2 at the bottom of the page, that the speed is reduced to 4.7 inches per second with 11 pound load. Is that a problem?
after emailing with the supplier i found that the duty cycle being 20 %, for every 4 mins of it being used it needs 16 min break, which is not OK. im looking for a more suitable one now.
What about a crank and connecting rod arrangement, like on a steam locomotive?
that was my first idea but i figured going with the arduino and actuator would be more accurate. so i found a new actuator Deluxe Rod Linear Actuators | 3-36" | Firgelli Automations this has a heavier load so the break time will much shorter. so with all of this in mind what will i need to be able to control the actuator?
What about a crank and connecting rod arrangement
that was my first idea but i figured going with the arduino and actuator would be more accurate
I think you should look carefully at the crank idea again. You can use a continuous duty motor and not have any duty cycle. Uni-directional so no H bridge required. Indeed, you can use a simple mechanical counter and perhaps a simple variable speed control and not need an Arduino at all. All in all less expensive and likely more robust.
ya i accounted not having to program any arduino or anything,the price difference between the actuator and the linkage idea would be minimal and i figured a linear actuator would be more fool proof then having to have parts made and put together. i am completely open to options though!
aarg:
What about a crank and connecting rod arrangement, like on a steam locomotive?
+1
Tomputt:
ya i accounted not having to program any arduino or anything,the price difference between the actuator and the linkage idea would be minimal and i figured a linear actuator would be more fool proof then having to have parts made and put together. i am completely open to options though!
check your pricing again. the linkage could be a simple bolt on a flywheel with shaft on the drawer.
a used treadmill motor/driver would be able to outlast a decade or use.
speed is also a considderation. if you run the flywheel at 10 RPM, that is 10 cycles a minute.
the linked actuator can open at 3 inches a second, or one full open/close cycle in 8 seconds, or 7.5 cycles a minute.
you will need relays or some such to power it as well.
if the drawer has wheels or rollers a windshield wiper motor turning the crank directly should be strong enough. Also cheap, fast and quite reliable.
I've used Firgellis in the past - easy to use, and depending on how you order/configure them, you won't need limit switches etc - as they have an option for an RC servo style interface.
Just stroke between the two end points and 'Bobs your uncle'
so is this everyone telling me to go with the linkage idea, or the linear actuator .
I like the crankshaft idea, but...
Does the drawer test method needs to mimic the forces that a real drawer would see when open and closed? That is, linear forces in one plane (horizontal). A crankshaft with the connecting rod coupled directly to the drawer would cause forces in 2 planes. To be a real world test the connecting rod would need to be coupled to a follower that would remove the second force component.