Solenoid Powered Omnibot Claw

Question

I was wondering, the way the Omnibot 2000 claws are set up, it seems a solenoid may be able to make them open with a spring acting to close them. Is this possible? and if so is it a good idea due to the fact that solenoids are usually high voltage and I can not seem to find a digital one, are they able to connect with the EZ-B? Please let me know if this is a good idea? Thanks.

Troy · Answer

Josh had an idea using small window door locks. You will have to check to see if it will fit though. I tried and failed at using a smaller solenoid so I put it on the back burner. As far as the power is concerned, you can use TIP or MOSFET to switch it on. Rich made a tutorial on how to make it from scratch. He has a bunch of other tutorials as well here. (Second post this time Rich) If you want a premade one you can find them on ebay. Here is one of them.

RobertL184 · Answer

There are lots of 12v Solenoids available. https://www.mcmaster.com/#solenoids/=ophk6i. Also some 5 volt ones like https://www.sparkfun.com/products/11015. Some have springs on them others do not. They are great for momentary activities, but you typically don't want them on long because they are battery eaters.

clintgarr75 · Answer

Oh wow, so I would connect a regular motor to the SMD MOSFET and then the MOSFET to the EZ-B and it will be able to control the motor just like it would a servo? This may be the answer I have been needing, I could just replace the motors in the Omnibot and connect MOSFET's to all of them and just use the gears that are already in the arm for it to move. I was thinking I would have to replace everything stock with servo's like D.J. and Mr. A did. will this work?

Dave Schulpius · Answer

If using DC motors and you want them to both go forward and reverse you should use an H-Bridge. Let us know your operating voltage and the how much amperage the motor pulls and we'll recommend a good h-bridge.

clintgarr75 · Answer

Using the MOSFET I can not just plug the Motor directly into the EZ-B?

Robot Doc · Answer

The MOSFET is controlled by a small low voltage 5 v that is supplied by the EZ-B ports. The MOSFET switches a larger voltage that is used by the motors and is not supplied from the EZ-B.

Troy · Answer

@clintgarr75, dschulplus is correct. For the purpose you describe you need the H-bridge for forward and reverse. For higher current motors, more than one mosfet (I think 4 per motor) are used in the H-bridge circuit. A single mosfet will give you one direction switching. I know Im oversimplying it but essentially you need an H-bridge. I'm sure someone in the forum can recommend one for the stock omni robot.

clintgarr75 · Answer

Ok, the arms of the Omnibot are really getting to be very tricky to work out, does anyone know a really simple solution for the Omnibot 2000 arms that doesn't require a degree in electrical engineering to figure out?

clintgarr75 · Answer

Sorry, the post above was a joke. I am just getting frustrated trying to make the Omnibot 2000 arms work. Thank you all for helping me, this information has given me a lot to think about. Thank you.

Danger! · Answer

@clintgarr75, I am not exactly sure how you want to your claws to work. If you use a solenoid, that will only move in one direction, a spring would return it. That sounds like what you were looking at. If that is the case, you could power it with a TIP as @Troy suggested, and Rich designed. You could also use a relay. They come on boards from two, to dozens. relays If you want to power it in both directions, you could use an actuator or motor. Then, you would need an H-bridge to switch from forward to reverse as @dshulpious said. actuators I have put together a diagram of how to make a simple H-bridge using two relays. I am going this route because I will have many motors, and putting in a few large relay boards in neater than a dozen separate H-bridges.  When both relays are in normal position, the motor is grounded on both sides. If you flip one, or the other, it will make that side hot, and turn the motor either forward, or reverse.

Troy · Answer

This may not be the best thread but it does have some good info on the shoulder. Thread link Btw, don't forget to credit Rich for answering your original question on solenoid use.

clintgarr75 · Answer

Thanks for all the help. I really appreciate all the help.

jstarne1 · Answer

Hey guys , the doorlock actuator is what I was going to use for my claws. They are easy to wire and have lots of torquehttps://www.amazon.com/High-Power-Door-Lock-Actuator/dp/B0002KR9PW/ref=sr_1_2?ie=UTF8&qid=1380476803&sr=8-2&keywords=door+lock+actuator+mini These were $ 3.90 so they are very cost effective , they need 12 volts and a relay can trip them or you could use tip120 Darlington transistors too.  There are micro or mini versions of this that are a few dollars more buy they are still cheap and strong.

Troy · Answer

They fit in the arm? I wonder what the return force is when not energized. That was the problem I had. Oh this may be a brushed motor, rack and pinion gear arrangement inside and not a solenoid. Do you know Josh?

Danger! · Answer

Thanks for that link Josh. That is a good price. I wonder if they would be strong enough for my B9 claws.

jstarne1 · Answer

@troy they are a brushed motor with gears. They are pretty strong especially if kept energized to hold something. I imagine a pwm could allow you to adjust holding torque too.

Troy · Answer

Those will be great if they fit.

jstarne1 · Answer

They are really small and there are even versions half that size for super tight installs.

jstarne1 · Answer

https://www.amazon.com/High-Power-Door-Lock-Actuator/dp/B0002KR9PW/ref=sr_1_2?ie=UTF8&qid=1380476803&sr=8-2&keywords=door+lock+actuator+mini

Here's a more compact model , they get about a inch shorter than this without being a special order part.

Troy · Answer

Great! I will save both. Let me know how yours fit so I will know wether or not to buy smaller ones.

clintgarr75 · Answer

Door Lock Actuator Motor Dorman 746-400 Would this word for the claw? It seems really small, but I don't know if it would have enough power to hold anything with Thanks,

clintgarr75

Upgrade to ARC Pro