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76  Using Arduino / Motors, Mechanics, and Power / Re: Attempting to make a computer controller Power Wheels toy, but new to electronic on: March 04, 2014, 03:25:28 pm
Besides a motor driver, something like this could be used to control the motors forward and reverse but you wouldn't have speed control.

Something like that could be used - but I wouldn't recommend it. Why? Because 12 volt PowerWheel ride-on toys have motors (there are usually 2 motors - one for each rear wheel - the 6 volt toys use a single motor) that can easily draw well over 10 amps of current; you'll quickly fry those small relays on that board. That said, you could use those relays to activate a larger pair of SPDT relays.

carpetfizz:

First off, I hope you included the 25 amp fuse (I believe it is a slo-blow fuse) when you switched out the battery; if you didn't - add it back in - connect it as close as possible to the battery's positive terminal - a small 6 inch pigtail holder like this is best:

http://www.superbrightleds.com/moreinfo/led-vehicle-replacement-bulbs/waterproof-mini-automotive-fuse-holder/768/1741/

That, or re-use the one that came with the original battery.

Secondly - I would drop using the car battery - especially if it is a standard wet-cell starter battery; while you'll get longer run time initially, in a short amount of time you'll destroy the plates on the battery as it wasn't meant for deep-cycle use. Instead, purchase a larger AGM or gel-cell SLA deep-cycle battery. They are more expensive, but are designed for running loads long-term like this toy.

I would also suggest getting a smart battery charger for the battery (instead of the one the toy came with) - a quality CTEK charger for SLA batteries (or something similar) is best - while more expensive, it will keep your battery in tip-top shape long term (do not use a car charger battery on SLA batteries - the charging current tends to be too high).

Since the fuse is rated at 25 amps, you want a motor driver of at least that much (and actually more), because those motors will pull that much when stalled (that's why the original fuse is rated in such a manner). As I said before, there are two motors, one for each rear wheel. In the PowerWheels toy, the two speeds (high/low) are governed via a clever switch arrangement on the speed "shifter" - the switches basically switch the motors between being connecting in serial vs being connected in parallel across the battery (I can't recall which arrangement is high speed and which is low speed).

I would recommend a couple of other places/items to look into which will be helpful - first, there is a whole community out there of PowerWheels (and similar toys) enthusiasts and modders - they like to do really crazy things with them, mostly as a way to have fun with their kids:

http://www.modifiedpowerwheels.com/

Also google "modified power wheels" for more...

Secondly - one of them has a very nice CD on some of the more popular mods - well worth the cost, as it brings together a ton of information (including patents and service manuals that would take a while to gather yourself):

http://powerwheelscd.com/

Ok - with that out of the way - you probably want to control this vehicle, right. Well, as mentioned, you need a motor driver of some sort. What you'll want to find, ultimately, is an h-bridge driver board that can handle about 30 amps. Alternatively, you could connect the motors separately - each will need about a 15 amp driver.

You can find such boards on Ebay, Pololu and other places - just make sure it can handle the amperage of the motors (also note that some of those boards may need a heatsink and/or forced-air fan attached to handle the current - and some don't come that way; you have to add it yourself - just read all the specs carefully).

As noted above, if you just wanted on/off control - you could use relays, but they would need to be able to handle the current. You could either use one of those boards from Ebay as mentioned, and either switch extra relays with them, or possibly install/hook up better relays - or you could build your own relay board. If you go that route, 40-60 amp SPDT automotive relays are fairly cheap and will easily handle the switching of the load. Just hook them up as shown in the relay tutorial for the Arduino and you'll be fine.

Two SPDT relays are hooked up so that the "common" leads of each relay go to each terminal on the motor, and the NC leads of the relays go to the battery positive terminal (via a fuse!) and the NO leads of the relays are connected to the ground (negative) terminal on the battery. Make sure that you use proper gauge wires between the battery, motors and relays (10-12 gauge should be ok), otherwise the wires will heat up, you'll lose current in them, and the motors will run slower.

Another hint/idea: If you set up your drive motors as seperately wired (so you can control the speed and direction of each) - while it is a more complicated setup, it opens the door to doing some potentially fancy things with your PowerWheels (for instance, an electronic differential and/or traction control!).

Steering will be your greatest issue to tackle - these ride-on toys were not designed with ease of conversion in mind. If you want to throw money at it, you can find fairly powerful servos or linear actuators out there that will do the trick (then all you need to do is figure out how to mount and connect the device to the steering system). Check out Servo City (http://www.servocity.com/) as well as Firgelli Automation (http://firgelliauto.com/) for ideas, just be prepared for sticker shock.

Whatever you do, don't go cheap or small on the gearmotor for actuation of the steering; it needs to be pretty damn robust. For my project, I used have a gearmotor from a drill powering a piece of threaded rod with a travelling nut to actuate my steering. Also - whatever you do, make sure that you have limit switches or some other means to cut the current to the steering motor for your testing and actual operation - if not, you'll either break the motor, or the steering system, or both (ask me how I know). A good limit switch circuit (and also shows how to wire the relays) is shown here - this is Zoomcat's circuit; he's a regular here on the Arduino forum's:

http://web.comporium.net/~shb/switch.htm

Be aware that the diodes, limit switches, and relays need to be sized for the motor current draw and voltage needs.

If you decide to build your own actuator, you'll also probably want some kind of position feedback; if you use a geared servo from Servo City, that will be built in, of course - but if you use a linear actuator, some may have pulse sensors (typically a hall-effect sensor or reed-relay actuated by magnet) or they may have a potentiometer that you can read. Some linear actuators ($$$) can be driven using servo signals, as well (in which case, you don't need to worry about a separate position sensor). Whatever you do, don't rely on the position sensor in lieu of the limit switches! If that sensor fails for some reason, the limit switches will be your backup.

The PowerWheels modifier community also has numerous instances showing how they modified their particular chassis for steering and R/C control - so look through the forums and other sources to get some ideas there as well.

Lastly - whatever you do - don't try to replace the motors with brushless motors of a similar size. While it is possible, the gearboxes aren't built for the higher RPMs and power those motors can generated, and you will end up burning through gearboxes as a result (and they aren't easy to get as replacement components).

Good luck with your project!
77  Using Arduino / Motors, Mechanics, and Power / Re: PWM ports can't drive motor properly. Possible hardware error? on: March 04, 2014, 02:44:34 pm
Have you tried testing the pin (10) with an LED/resistor to see if you can vary the brightness of the LED to verify that PWM is working on that pin?

Also - what about the rest of your code, is it doing anything that could alter pin 10 PWM output?

Finally - what version of the Arduino IDE/software are you using?
78  Using Arduino / Motors, Mechanics, and Power / Re: controlling 10A DC Motor using Arduino UNO on: March 04, 2014, 02:38:41 pm
Actually, you wouldn't really need a transistor to control a relay. Most hobbyist grade relays will operate at +5V, which is perfect for toggling with any Uno pin. A relay is probably the way to go, though.

Yeah - but most relays draw far more current than the recommended 20-40 mA that an i/o pin can provide; that's why a transistor or mosfet is used. The only relays that do have such low resistances to allow "direct drive" (and you should always have the flyback diode involved regardless) tend to be so-called "reed relays", and they generally don't have contacts rated for a 10 amp inductive load.

So, not taking into account the actual power management systems and the other rails of the PSU, a 300 watt ATX power supply could easily source > 10 amps, hardly what I'd call a large PSU.

Something else to consider - some PC power supplies don't like inductive loads (ie - brushed DC motors and the like) connected to them; the large inrush current will sometimes trick the supply into switching to a "shutdown" or "safe" mode. Not all such supplies, but it does happen. For these kinds of supplies, you either need to add a large electrolytic capacitor to the DC output and/or set the motor driver up to do a "soft start", slowly (comparatively) ramping up the speed of the motor to prevent the inrush current from tripping it.
79  Community / Bar Sport / Re: Airplane Design / Safety. on: March 03, 2014, 02:09:39 pm
One of my favorite "stories":

http://en.wikipedia.org/wiki/Gimli_Glider
80  Topics / Robotics / Re: UGV robot motor shield problem on: March 03, 2014, 02:05:36 pm
You will not likely find a "shield" that can handle a 12A "running" current and a 79A "stall" current motor. Finding something for two of them - good luck.

You can, however, find a motor driver board that you can connect for such specs. It won't be inexpensive. Don't try to cheap out on this, either - unless you like fire and wasting money.

Normally, I point people toward Pololu - but this time, they don't seem to have anything that would fit your requirements. The difficulty is finding something to match that stall current; 79A is not anything to sneeze at. Since such a stall current occurs (however briefly) at startup, you need something that can handle it for a short while. Ultimately, you want to size your h-bridge to be a tad larger than the stall current ratings (10-15%) - which in your case would bring you close to 100A.

At that point, looking at something like these controllers (likely the RDFR33 - which should handle two motors with a 95A surge, and 35A continuous):

https://www.vantec.com/acatalog/spdcat.html

Unfortunately, such a controller isn't anywhere close to "inexpensive".

Building such a controller is likely out of the question; when you are dealing with currents above about 10A or so, things get really tricky with h-bridge designs - anything homebrew will likely be a matter of burning up a bunch of expensive parts before you get something stable (and even when you think you have something stable, you may find it going up in a puff of smoke and fire when you least expect it).

I can't even recommend a relay circuit to you, because while such relays (well, at those current levels, they're going to be called "contactors") do exist, purchasing such will likely run you as much as the vantec controller, and you won't have PWM speed control, either (unless you add a bunch of high-current n-channel mosfets or IGBTs to the low-side - and at those currents, that might just be asking for trouble ultimately).

You might want to re-think your design to try to use a more reasonable motor - that, or increase your budget.
81  Using Arduino / Displays / Re: 132x32 graphic LCD on: March 03, 2014, 01:46:09 pm
Here's something - there's a link to a RAR archive that appears to contain everything needed (better datasheet, source code, etc):

http://ram-e-shop.com/oscmax/catalog/product_info.php?products_id=1616

...for the future, if anyone needs the file and the above link stops working, let me know - I have a copy.
82  Using Arduino / Displays / Re: 132x32 graphic LCD on: March 03, 2014, 01:42:44 pm
You might be able to find something here:

http://www.topwaydisplay.com/TechnicalInfo/index.htm

This display doesn't seem to be one they currently manufacture...
83  Using Arduino / Project Guidance / Re: Using Camera Component from USB Webcam on: March 02, 2014, 11:43:18 pm
The arduino is an 8 bit micro controller, how many 1980's computers do you know that had web cams on them. I will tell you zero.

Actually - barring the "web" part of things, I had a digitizer cartridge (DS-69A) for my TRS-80 Color Computer 2 - took forever to capture an image, but it did work...
84  Using Arduino / Sensors / Re: Simple angle measurement on: March 02, 2014, 01:55:55 pm
Have you thought about using a capacitive tilt sensor?

They used to use these back in the day (80's/90's) for 3DOF head tracking sensors (pitch/roll mainly - yaw was done with a compass) before gyros/accelerometers became cheap.

Basically the sensor had a liquid electrolyte and some terminals; one set of terminals was excited using an AC signal, and the other set could read the signal which would change based on the tilt level (which would alter the capacitance). At least, I think that is how they worked (?).

They suffered from "settling" issues - in which if tilted too fast, the liquid would take a while to settle - so that limited read rate (plus they had a limit as to how far they could be tilted, of course).

I'm not sure if they are still available (as a component) or not...
85  Using Arduino / Motors, Mechanics, and Power / Re: RC-Reciever to Servo -- Problem with RC-Lib on: March 01, 2014, 11:31:42 pm
First off - I have never used this library - so this might be the "blind-leading-the-blind" - that said...

...I have to ask - what version of the library are you using?

Because in the examples I see that come with the latest version of the library - specifically the examples referencing ServoIn and ServoOut - neither one of them show the setup and use of an ISR routine or a pin-change interrupt.

I tend to wonder if somehow that may be related to the issue you're having?

Beyond that, I can't offer anything else, other than to ask whether you have successfully been able to execute and use the "ServoOut" example that comes with the library (which seems to be the closest library example to what your example code is doing)?
86  Using Arduino / General Electronics / Re: Are shift registers "relatively new" chips ? on: March 01, 2014, 11:13:59 pm
Shift registers are not new.

The very concept of the shift-register has been around forever. While I've never studied it, there had to be some form of a shift register (both for input and output) in early delay-line (mercury and otherwise) machines; heck, I think that technology original came from early radar systems.

I'm also pretty sure similar ideas were embedded in some of Korad Zuse's designs; I'd be willing to go back as far as Babbage's machines, mechanically (some kind of shift-mechanism was likely needed to transfer information back and forth between the mill and store, for instance).
87  Topics / Robotics / Re: Does a PowerWheels motor need to be powered by a chunky 6v? on: March 01, 2014, 02:24:38 pm
Ok,  thanks. I was just wondering about that. I still would like to use that motor for some other project, so I'll just get the proper battery for it when I figure out what I'll do with it.

Just make sure when you do get such a battery, you hook up a fuse (or circuit breaker) near the positive terminal of the battery, so that it trips in the case of a short or fault. Such batteries can easily pump out well over a hundred amps of current for a short time, vaporizing wires, starting fires - and, in the rare case where the short or fault is over a conductor capable of handling the current - the battery itself can explode.
88  Using Arduino / General Electronics / Re: Cheap power strips on: March 01, 2014, 02:19:52 pm
On cheap power strips I have seen, that is how they are generally set up; most recent ones also include a reset-able circuit breaker rated at 10-15 amps or so. Some also contain voltage spike protection, and maybe a light to show that the power is on to the strip.
89  Topics / Robotics / Re: Does a PowerWheels motor need to be powered by a chunky 6v? on: March 01, 2014, 12:18:09 am
Out of curiosity, what would I need to power this motor using the battery charger as previously suggested? Is it just a matter of connecting the motor directly to the charger as if it was the battery?

No - generally a "dumb" battery charger for an SLA battery is limited to 600 to 800 mA; while the motor may start to turn with no load, it more than likely will just sit there, and potentially burn out the charger.

What you need is a power supply capable of supplying at least several amps in a short burst, and then 1-2 amps continuously - even then, this would only be enough to run the motors with no load on them.

If you want to be able to have some kind of load on the motors, then you need to supply the proper amperage - likely around 25 amps.

Your difficulty will be finding a 6 VDC power supply capable of outputting such amperage (if it were a 12 volt system, you could use a cheap 50 amp car starter/battery charger).
90  Using Arduino / Motors, Mechanics, and Power / Re: Arduino Relays - strange issues on: February 28, 2014, 05:00:16 pm
Okay, now I'm no longer 99% certain it is a NPN, but 98%.

What are the markings on the transistor? If you look those up to get a datasheet, that will tell you...
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