I have a project I am working on that requires the 5 linear actuators to work in sequence to complete two task. I’ve been trying to figure out how to make this happen. So far I came up with the idea of using a car alarm module and having a combination of standard relays, latching relays and time delay relays to preform the task then another set to reverse the task. I have a problem with reliability and complexity because if any one relay has a problem it could potentially destroy what is being moved. So I’ve stumbled across arduino.
My question is can arduino be programmed in a way to follow a automatic sequence then reverse the sequence?
For short hand purposes I’ll type LA instead of linear actuators
The sequence would be
Push button
Retract LA 1&2
Extend LA 3&4
While extending 3&4 extend 5. Extending 5 needs to happen mid stroke of 3&4
End
Then the reverse sequence
Push button
Retract 3&4
While retracting 3&4 retract 5. Retracting 5 needs to happen mid stroke of 3&4.
Extend 1&2
End
I understand I would need to learn the coding of it all and I have no problem doing that. But is this the right platform to perform these task?
Yes, from what you said so far, Arduino would be a good choice.
Can you post a link to technical details of the LAs. Voltage, current, connections, that kind of thing.
The "mid stroke" thing might be slightly tricky. How would the Arduino know when the LA is at mid stroke? It could be timed, but if the supply voltage changes, such as from a battery that is low on charge, timing might not be accurate enough. Some form of switch that gets actuated at the mid point of the stroke might be better.
It has a feedback so you should be able to use that to know where you are, so trigger the movement of #5 when #2 and #3 are halfway.
You'll also need this feedback if you want to keep them in sync.
This are pretty powerful actuators - up to 5A current at 12V. It's a brushed DC motor so that bodes well for PWM based speed control, and you should be able to use an H-bridge for direction control. Not sure if you can find H-bridge ICs for this current, you may have to build your own.
Yeah I’ve noticed that the amperage rating for some of the boards is relatively low. Would it be ok to use the Arduino to trigger relays? That way the relays are taking the load of the LAs
It depends how closely in-sync you need to keep the LAs. If it's super-critical, then PWM controlled H-bridges will be required. If it's less critical, then relay bridges should be easier, especially for a beginner. If one of a pair of LAs gets too far ahead of the other, the Arduino can pause it until the other catches up. If sync is not critical, then a single relay bridge can drive a pair of LAs and one of the feedback lines can just be used to detect the half way point.
If using relays, its much easier if you get relay modules with built-in driver transistors. An Arduino output cannot drive a relay coil directly.
For example these relay boards have built-in drivers. The contracts are rated for 10A @ 12V, so fine for individual LAs, but for driving pairs of LAs, they are right on the limit for current.
Worked a couple of years designing linear actuators. We also did pneumatic cylinders.
Drawing shows limit switches on it, but don't see anything for a pin out. You can use those to know when you are full stroke without having to poll A/D for the pots. Just look at the one you need to for mid stroke.
Pololu sells motor drivers that can easily handle those actuators. I've been using this one for several years with a very similar actuator to open/close heavy greenhouse vents.
Keep the 25% duty cycle limitation of that actuator in mind.
I think you are over complicating the project. I recall my old MB 300SD had two hinge points on each side of the hood so as the hood opened, it also moved forward. It even allowed the hood to stand vertically. That would sure be easier than using linear actuators. OF course, the hinge method could not be operated remotely.
I have had other vehicles with the hood hinges in front, near the radiator. Not necessary to move the hood forward to open.
I agree. 5 expensive 5 Amp linear actuators just to lift the bonnet of a car? That seems totally over-engineered!
Surely there is no need for expensive LAs with feedback here? Nothing is critical in terms of position or load bearing. If hinged correctly, the bonnet should stay clear of the other bodywork without using an actuator for just for that purpose?
The actuators you plan to use are $130+ each. There must be simpler LAs with lower currents and without position feedback that would be more than good enough for the job?
This certainly isnt my field of knowledge and I welcome suggestions as far as components to use. But as of right now the method is the method. Nothing on this car is factory. The hoods on these cars never opened this way. Originally they were a gull-wing design opening from the sides. This was not an option with the width of the engine. The cost of the LAs is a non point. $600 in actuators isnt much on a $200,000 car. Is it over engineered? Yes, the whole car is. But having a "wow factor" is far more important to this customer. We could have easily limited the hood travel and not have to push the hood forward. But, the customer wants what he wants.
Scottmh:
This certainly isnt my field of knowledge and I welcome suggestions as far as components to use. But as of right now the method is the method. Nothing on this car is factory. The hoods on these cars never opened this way. Originally they were a gull-wing design opening from the sides. This was not an option with the width of the engine. The cost of the LAs is a non point. $600 in actuators isnt much on a $200,000 car. Is it over engineered? Yes, the whole car is. But having a "wow factor" is far more important to this customer. We could have easily limited the hood travel and not have to push the hood forward. But, the customer wants what he wants.
I get the same problem from time to time! Usually it is a customer wanting a cheaper way with a cheaper part, like from Ebay!
May I suggest you construct a test structure to emulate the car hood and body, and get all the supporting structures, mounting, etc. and the software done before actually attacking the hood? It's not going to be easy to get both ends of each LA mounted with pivots at the ends so they move with the hood.
Keep us up to date with the project. Looks very interesting!
Linear actuators are pretty simple. But you need a "bridge" of some kind. Strictly speaking, they are called "H-bridges". An "H-bridge" is the circuit needed to allow the LA to run in both forward and reverse directions. Either a chip/board like the one suggested earlier, or one made of two SPDT relays. Look for tutorials for running DC motors in both forward and reverse by using an H-bridge. Essentially that's what is going on inside a LA.
Well I’ve officially started this journey. I received my arduino mega beginners kit and ordered a Multimoto shield. I’ve been non stop reading about programming. At this point I just need to sit down and grind some code out and see what happens! I appreciate all the help you guys have given me and pre thank you for the help to come haha
