Remote controlled Power Wheels Jeep project

[kjh83]

Long-time lurker here.  I'm starting a project and figured it might be a good time to bounce some ideas around, and share more details if people are interested.  I'm adding remote control (among other things) to one of these:
http://fisher-price.mattel.com/shop/en-us/fp/power-wheels-jeep-vehicles/power-wheels-hot-wheels-jeep-wrangler-cbg61

Some ride-on cars have remote control right out of the box - in fact we had one.  But the parts availability just isn't there like it is for the Power Wheels brand cars.  I discovered this when I needed replacement parts for the one we had.  On the plus side, I learned how to do rudimentary plastic welding using a soldering iron since replacement parts were unobtanium.

At this point I've got the Jeep, an arduino, a bunch of components, and a bunch of parts arriving little by little.  Aside from the programming and radio communication aspect, the biggest hurdle will be hooking up the mechanics of the steering linkage.  I looked at a bunch of gearboxes on aliexpress and made a full-sized mock-up of the one I thought would work, but I won't know for sure until it gets here.

Nothing came up in the search - so has anyone here done something like this?  Thoughts or ideas?

[mdszy]

Why go through the effort of doing the radio control/programming stuff yourself? Look into RC car receivers. Those will take care of the radio control stuff for you. You can then connect servos and speed-controllers to the receiver. The speed controller(s) get connected to brushless motors for the powertrain and the servos can be used for steering.

[KMoffett]

I modified a Power Wheels Jeep for one of our Computer Science Professors. This one was autonomous.

Ken

[kjh83]

Why go through the effort of doing the radio control/programming stuff yourself? Look into RC car receivers. Those will take care of the radio control stuff for you. You can then connect servos and speed-controllers to the receiver. The speed controller(s) get connected to brushless motors for the powertrain and the servos can be used for steering.

I considered going that route but I'd like more granular control, as well as bidirectional communication. For example, it might be nice to have the car's battery level displayed at the transmitter.  And with an arduino I can add things like soft start or a remote kill switch with a few lines of code instead of being limited to what the RC receiver can do.

More importantly, it gives me a fun project I can do with my kids.  I could do some things with an off-the-shelf setup, but I'd also run up against its limitations pretty quickly.

[kjh83]

I modified a Power Wheels Jeep for one of our Computer Science Professors. This one was autonomous.

Ken

That looks pretty neat.  Are there any videos of that running?  I looked at using a linear actuator, but it would seriously blow the budget - and there'd be a lot of pressure to get it right the first time. Those actuators probably cost more than I paid for the Jeep, whereas the gearbox I ordered was under $11 US delivered.

[KMoffett]

I do have videos (~18Mb each), but I don't have any posted for internet access.

Ken

[BrianHG]

I looked at using a linear actuator, but it would seriously blow the budget - and there'd be a lot of pressure to get it right the first time. Those actuators probably cost more than I paid for the Jeep, whereas the gearbox I ordered was under $11 US delivered.

At 15$us - 30$us for DC motor linear actuators at Alibaba, free shipping, I think that any other RC remote-control itself should blow your budget.

Though, with the Arduino, you can add a potentiometer to the steering wheel to an AD input to be used as power steering when the car is used in manual drive mode.

[kjh83]

I do have videos (~18Mb each), but I don't have any posted for internet access.

Ken

How did that linear actuator work out for you?  Do you remember what kind it was, or what the travel/gear ratio were?  If the $10 gearbox doesn't work out, I'll need a backup and a linear actuator might be easier than a servo, if I can find one cheap enough.  I checked AliExpress and the cheapest linear actuator was almost $45 shipped.

FWIW, here's a thread where someone used a "linear servo" on his Power Wheels Corvette similar to what you did:
http://forum.modifiedpowerwheels.com/viewtopic.php?f=26&t=17786

I'm also kind of curious about your project.  I have a toy tank chassis coming in that I'm going to make autonomous, but a lot of that code could just as easily be used for the Jeep.

[kjh83]

I looked at using a linear actuator, but it would seriously blow the budget - and there'd be a lot of pressure to get it right the first time. Those actuators probably cost more than I paid for the Jeep, whereas the gearbox I ordered was under $11 US delivered.

At 15$us - 30$us for DC motor linear actuators at Alibaba, free shipping, I think that any other RC remote-control itself should blow your budget.

As I mentioned above, the cheapest linear actuators I found on AliExpress were $45 shipped.  I tried looking on Alibaba but I can't make heads or tails of that site (couldn't even figure out how to sort by price).  But I just checked banggood.com and they had some in the $30 range, so maybe other websites out there have cheaper options.

Though, with the Arduino, you can add a potentiometer to the steering wheel to an AD input to be used as power steering when the car is used in manual drive mode.

If I understand you correctly, you're saying that I could disconnect the steering wheel from the steering linkage and have it controlled electronically.  Interesting.  That would make it a lot easier to override a child steering the car.  But I'd be concerned about safety if the power fails on a hill or something.  I suppose a clutch could accomplish the same thing, but that's getting way beyond the scope of the project.  Something to think about though.

[BrianHG]

Though, with the Arduino, you can add a potentiometer to the steering wheel to an AD input to be used as power steering when the car is used in manual drive mode.

If I understand you correctly, you're saying that I could disconnect the steering wheel from the steering linkage and have it controlled electronically.  Interesting.  That would make it a lot easier to override a child steering the car.  But I'd be concerned about safety if the power fails on a hill or something.  I suppose a clutch could accomplish the same thing, but that's getting way beyond the scope of the project.  Something to think about though.

Note that with the steering actuator, if power goes out, the steering will be locked in what ever position the actuator happened to be at that moment.  Those thing are like a solid stick, they cant be shrunk or expanded unless you power their DC motor.

I would still recommend a separate battery for the arduino itself with it's own battery so it wont ever crash due to the current draw during driving, and as your battery goes low, only the speed of drive and top steering speed will drop.

You could always put a strain gauge connected to the arduino on the mechanical steering linkage and create a system similar to a real car's power assisted steering.  If power goes out, you still have that mechanical connection.

[hendorog]

Why go through the effort of doing the radio control/programming stuff yourself? Look into RC car receivers. Those will take care of the radio control stuff for you. You can then connect servos and speed-controllers to the receiver. The speed controller(s) get connected to brushless motors for the powertrain and the servos can be used for steering.

I considered going that route but I'd like more granular control, as well as bidirectional communication. For example, it might be nice to have the car's battery level displayed at the transmitter.  And with an arduino I can add things like soft start or a remote kill switch with a few lines of code instead of being limited to what the RC receiver can do.

You might just be a bit out of date
2 way R/C is common now and the Taranis has open source firmware:
https://github.com/opentx/opentx

https://www.rcgroups.com/forums/showthread.php?2178865-FrSky-Taranis-with-OpenTX-2-0-and-beyond

[kjh83]

You might just be a bit out of date
2 way R/C is common now and the Taranis has open source firmware:
https://github.com/opentx/opentx

https://www.rcgroups.com/forums/showthread.php?2178865-FrSky-Taranis-with-OpenTX-2-0-and-beyond

Interesting, but it seems expensive and doesn't give me the flexibility that something like an arduino does.  The finished result will probably look nicer though.

[hendorog]

You might just be a bit out of date
2 way R/C is common now and the Taranis has open source firmware:
https://github.com/opentx/opentx

https://www.rcgroups.com/forums/showthread.php?2178865-FrSky-Taranis-with-OpenTX-2-0-and-beyond

Interesting, but it seems expensive and doesn't give me the flexibility that something like an arduino does.  The finished result will probably look nicer though.

Yeah its horses for courses.

The R/C approach would allow you to do a much simpler conversion using standard RC components for the most part. Would get you up and hooning around the lawn fast just using plain old RC control before you move on to write custom firmware.
Getting jollies quickly is not a bad thing for a kids project (and of course one where any sort of manager is involved )
Kids will still see it as a fun project, they normally don't care about who wrote the firmware like we do

Arduino approach trades off development time for much more flexibility.

[kjh83]

Yeah its horses for courses.

The R/C approach would allow you to do a much simpler conversion using standard RC components for the most part. Would get you up and hooning around the lawn fast just using plain old RC control before you move on to write custom firmware.
Getting jollies quickly is not a bad thing for a kids project (and of course one where any sort of manager is involved )
Kids will still see it as a fun project, they normally don't care about who wrote the firmware like we do

Arduino approach trades off development time for much more flexibility.

Yeah, my son doesn't really care about adding R/C.  That feature is for me so I don't have to stay a few feet behind him to make sure he doesn't cause havoc.  He's just happy to drive it.  There's a lockout screw that enables 5 MPH (as opposed to 2.5 MPH) and I removed that and let him go full speed once.  When he got to the other side of a field and decided not to come back is when I decided that 5 MPH will only be enabled again once the remote is set up - even if it's just controlling the throttle initially.  Chasing after a toddler zooming around in a little Jeep is exhausting, and looks ridiculous.

So the R/C isn't for him.  I think he'd be thrilled just having an ignition key that works.  The R/C ride-on car we had had a plastic key that went into the ignition and when turned, the car turned on with headlights and an engine revving sound.  This: (click) is what the Power Wheels has.  It doesn't even come out.  Well, I yanked it out so I could find a functional replacement (still looking) but it doesn't do anything except sit there.

But at no point should the Jeep be non-functional, even while in the intermediate build stages.  I'll either tie into the existing wiring, or run a secondary set of wiring that can be removed if needed.

[KMoffett]

A simple key fob remote with a cut-out latching relay for a remote kill switch.
http://www.northshorecommercialdoor.com/emxlrloratr1.html?gclid=CLe_kY63vdQCFQKewAodqeUIFw
Maybe even add a tilt switch function, in case of a rollover, to that.

Ken

[kjh83]

A simple key fob remote with a cut-out latching relay for a remote kill switch.
http://www.northshorecommercialdoor.com/emxlrloratr1.html?gclid=CLe_kY63vdQCFQKewAodqeUIFw
Maybe even add a tilt switch function, in case of a rollover, to that.

Ken

I thought about going that route at first, but if the signal can't get to the Jeep or a battery dies then it doesn't work.  I'm just going to send a pulse every second or so, and if the Jeep doesn't get it it'll shut down the drive motors.  So if I don't have the option to control it, it won't move.

There may be off-the-shelf components that do some of the things I want, but the best way to do this really is using something like an arduino. 

[kjh83]

A little update.. I finally got everything together and went to try the motors out with the motor controller I bought from AliExpress, and it turns out it's junk and heated up and stuttered once the motors started spinning [slowly].

A little searching found this, which shows that this is a common problem with the controller I was using:
https://www.xsimulator.net/community/threads/cheap-chinese-monster-moto-clones-and-problems.9059/

So now I'm trying to figure out what kind of brushed motor controller to use instead.  I've preliminarily narrowed it down to two:

http://www.hobbywing.com/goods.php?id=357

https://www.pololu.com/product/2515

The Hobbywing ESC goes for under $30 delivered, and is supposed to handle 60 amps, and the Pololu is $50, but has the advantage of having two distinct channels (@ 18A/channel) so I could do a software differential if I wanted to.  I'm keeping the motors stock so I won't be going over 30 amps continuous.

The problem is that I'm not trying to spend too much money on this project, but decent high-current motor controllers aren't cheap.  If I could find a simple high-current, no frills H-bridge setup I'd be thrilled.  Anyone know of such a thing?