Main Goal : To listen for a knock at the door and then notify the human occupant of the house. Eventually will be an AUV, complete with charging station.
More pics this weekend I’ll post more pics this weekend and a possible Walk Through on a problem I was having. Basicly, the solution is to be a smarter techie, and work things out ahead of time. Right now, writing some data logging code for the accelerometer, because right it’s like I’m flying blind trying to get Leo to drive in a straight line.
Well, got Leo back together completely and now have a short somewhere in the drive board. I unplugged the arduino and it’s getting power still. I don’t know if I bridged something in the drive board or what yet. I’m thinking that is where the problem is. Will find out later today.
It might not be a short at all, are you still using L293Ds? As far as I can tell, they use CMOS buffered inputs, which can ‘float’ if left unconnected. That means the inputs won’t return always to logic low if you remove the Arduino.
You can solve this by adding pull-down resistors (around 10-20kΩ or so) between the L293D inputs and ground.
I hooked it back and now it’s doing nothing. I’ve got the batteries on the charger, because the L293D needs at least 5v coming into it to power the motors. I checked my board and it seems alright so far, will check things this evening, when I get a chance to look at it again.
Thank you for reminding me about about the fact that it can ‘float’ if not grounded. I learned about the ‘float’ on the L293D the hard way, when I first got it. I was very upset after connecting one motor, watching it oscillate, and not respond to the commands from the arduino, LOL. After connecting both motors it worked great, till now. Hopefully I didn’t smoke the chip. If I did, I’ll order a few this time and work on something else for awhile. I hope I didn’t, but if I did, it’s a learning experience. I think from now on though I’m going to run the outputs through diodes and setup a separate power source for the motor board and sensor suite, to help protect the main board from frying.
My next bot is going to be bigger, lol. Working on Leo is akin to surgery at times, trying to get everything routed and put it without killing something or my fingers is tough at times. His insides are a bit bigger than an index card.
News on Leo Good news, the arduino seems ok, bad news is that the L293D smoked itself. Still trying to figure out how and why. Not finding any shorts on the board and the voltages were well within.
**Current ** Check out Pololu’s info on the motors in the track drive. They stall at 2.1 A at a 3 volt level, will only be more at a higher voltage. The L293D is good to about 600 mA, continuous, 1 A peak. Also, running the motors at a higher voltage will burn them out quicker too. Pololu has a couple replacements, here and a Solarbotics one.
Found the short in the board It seems that the short is in the board. Either things got really hot and melted the plastic coating off the wires or the soldering iron got too close and heated them up. Time to redesign that board and start again on the accelerometer coding. I haven’t checked the chip yet, but maybe it’s still good.
Checked the chip I smoked it good and created a short from the inputs directly to the outputs via the power pin, ie you apply power and you get it out on the output pins. Good news is that more chips are on the way and I’ve had a lot of time to think of how to avoid this situation. Don’t route negative and positive wires over each other where things get hot, eventually they get too hot, the insulation melts and they short together and while draining the batteries they heat up the circuits big time!
Laying out some thoughts(copied from my blog on blogger) Ok to keep Leo moving in the direction he’s supposed to be I’m going to use:
A1302 Hall Effect Sensors on his front idlers coupled with magnets to give feedback on his track speed.
2125 Mesmic Accelerometer is used to detect and calculate drift on carpet, smooth floors, track skidding and bumps in the floor.
Even with those, there is still going to be a lot of error from track skidding, carpet nap, bumps in the floor, track wear, and from not being put back down exactly where he got picked up.
Going to use a PING(or other sonar type sensor) and a sharp or two map out his local environment to cross reference with his internal map. Basically, trying to program Leo in a fashion that biologicals think or at least my poor understanding of how I perceive my self and others do things.
Voltage monitors will be implemented as well so that Leo just doesn’t ‘die’ in the middle of the room. He will know when to return to his base(home) to re-charge(to eat). So will have to figure out how to get a charging circuit into his little body as well as everything else.
Ok got the parts in today, though not going to do anything with them tonight, a bit warn out and don’t want to smoke a chip because I was too tired. I still forgot to order a push button for Leo. It’s primary purpose will be for filming, ie set up camera, pushbutton, get in position, hit record right before the delay function times out, delay function times out, Leo starts and the filming begins. Oh well, next order or when I go by a radio shack.
Yay! That I got the parts in Now I can start building again!
Ok, I couldn’t resist I couldn’t resist and put in the new chip tonight. The left side works great, the right side has a bad connection that is going to need some work with the iron to fix, other than that I think Leo will be fine in a few days.
Still having problems Well still having problems with the drive board. Not sure what to do next, I have the parts for another arduino in, as well as another drive board. So half tempted to build those up and skip the trouble shooting process
Cool idea Very cool idea, but a bit far for me right now. I did think of a picaxe hooked up to a blue tooth, that way I could msg my door to unlock and open…a bit silly right now though when I just got Leo’s motors running again. On to my next post with that
Well Fedex anyways. They should be here on the 11th. I ordered 14, to make it worth the shipping. I figure with the popularity of the tamiya gearboxes and using dual H bridges like the L293D and the like, that some may want to swap for sensors or something.
Still no word on the China shipment of stuff though.
Well, got word that the china shipment, which is actually from Thailand(my fail) is at the post office. And basically starting over with Leo. The Tamiya dozer body is getting cramped on the inside and I still have more to I want to put in. I have two choices, build up and out and skew the center of gravity upwards or design a new body for him. The latter would be easier, because it’s just a box with holes big enough for the tracks, front idler and drive wheels to go through. His body would grow to 6x8, he’d have enclosed tracks, I would not be performing surgery when I started mounting all the stuff inside of him.
Got the stuff from Thailand, good stuff and now to test some stuff woot!!
Well did some testing on the arduino and it seems the PWM part of it torched. After I get some more work on the new drive board I will start on the freeduino clone I’ve got planned out. It’s basically an arduino that has screw terminals instead of female headers. I specifically designed to survive the shake test, IE pick up your bot, shake it hard, put it back down and see if it still functions. Yeah, I got frustrated putting wires back in the holes and decided to fix it. Also my design is a bit in the direction of being able to embedded in something and not have direct user contact, can we say sweet or what?
More detailes?