Len_Fixit,
No, I was thinking of something a little different. The ESC I’m using is a Dynamite Tazer, it has a power switch connected to it. I do know that it is ok to charge a battery as long as this switch is turned off. I was thinking maybe I could have a servo in the docking station that flipped this switch off, starts the charge, and then turns the switch back on. Contacts can be wired directly up to the battery. They will make contact somehow with the dock.
ahh… sounds even better, nice and simple.
Swap the switch on the ESC for a lever operated snap action type switch, would be easy to extend the lever for a larger contact area for the servo. Then a second switch on the charging dock operated by the same servo to start the charger, how about having this switch control a relay that has a short delay to ensure ESC power is off first?
Len_Fixit,
Yeah thats what I was thinking. I had not thought about the servo controlling the charger, this method seems even simpler by only having 1 servo to control both. I like this way! A delay might be able to be implemented by just placing the dock switch at a different position so that the servo horn does not hit both at the same time.
How about this… a base plate with a overhead section a little higher than the hood, servo and switch mounted to the overhead, large contact areas for the charge point.
A pair of sprung levers mounted on the front of the car for contact with the plates on the dock (LED on car to indicate contact). The ESC switch (red on image) mounted under the hood, possibly under a large sprung lever/plate. I would also be tempted to mount a second switch under the hood, setup to isolate the charging contacts when driving (to prevent shorting should they come into contact with anything metal).
Switches mounted on the hood would have less chance of accidentally contacting with an object when driving, and could be seen from the camera.
Len_Fixit,
That looks great! Exactly what I was dreaming up. I think this setup would be nice because it doesnt really require many modifications to the r/c vehicle.
Now all I need to do is get some server code going so I can run this remotely. Running video over remote desktop is just too slow…
Are you using RoboRealm? What’s to slow? Also, are you processing wirless video input and sending it back to you bot wirlessly? I’m interested in vision for my bot and want to know more about it.
Thanks.
I’ll be doing a similar thing with an upcoming project:
prod.campuscruiser.com/PageServ … wyMTY4MjU0
I didn’t intend it for autonomous charging (hard to get a biped to walk to exactly the right spot), but it wouldn’t need any changes to function as one.
Hmm… now that I look at it, it doesn’t seem to be a very straight-foreward schematic.
:X
Basically, all it does is use an FET (Q1) to turn off the robot’s servos if any of three conditions occur:
(1) I connect a charger to it.
(2) The microcontroller detects that the battery voltage has dropped below a value that I’ll determine in the software (probably 5.5V or so).
(3) The comparator ( U8 ) detects that the battery voltage has dropped below 5V.
LiPo batteries need to be kept from overdraining, thus the need for the last two conditions.
I chose to use both hardware (comparator) and software (micro) because I’m paranoid.
All the rest of the junk in the schematic is trivial.
The OR gates make the FET turn off if ANY of the above 3 conditions occur.
And, the charge pump IC in the middle of the schematic is just there to get the FET’s gate voltage up high enough to turn it on.
You might want to consider a simpler version of this setup, as FETs may have advantages for ya.
A MOSFET has very very high current capabilities (the normal package can take up to 75A with exceptional cooling, and many MOSFETs exceed even that).
More importantly, though, they’ve got really low resistance when turned on (on average, between a tenth and a hundredth of an ohm).
Any resistance in series with your circuit will produce a voltage drop and dissipate heat.
Perhaps relays are all you need for your application, though.
Those links do not work nick. For get to pay the bill?
JK 
The links work for me, and I’ve enabled the picture for “public” viewing…
That’s what I get for going to a community college.
I used the college storage because putfile isn’t working for me, any more.
I’ll go sign up for image shack and repost a link.
This is the error page that I get:
" CampusCruiser has experienced an application error. Please try again later.
If the problem persists, please report to your college Help Desk.
"
That’s Middlesex for ya.
Here she be:
img99.imageshack.us/img99/6020/minimebipedvb8.th.jpg
While I was at it, I changed some things.
Now it’s got the ability to check the voltage of each cell seperately (both in hardware and software).
What’s even better, my micro will be able to continously compare the two cell voltages and determine if the two are close enough to safely operate.
That way, if they’re not balanced, the micro can stop them from functioning.
Yep, I’m paranoid.
Oh, and I forgot to mention in the post above that there’s an onboard 1.2A battery charger, as well.
All that I’d need to do is hook up 9V to this bugger.
You might want to look into battery charger ICs if your battery doesn’t have an insanely huge capacity.
A lot of them are really really small and can charge at decent currents.
The revised list of possible cut-the-battery-supply conditions now are:
(1) Charger hooked up.
(2) Micro finds cell 1 to be too low.
(3) Micro finds cell 2 to be too low.
(4) Micro finds the difference between the two cells to be unsafe.
(5) Comparator finds cell 1 to be lower than 2.7V.
(6) Comparator finds cell 2 to be lower than 2.7V.
Very cool Nick. Have you started the layout of this board? I would like to see it when or if you decide to draw one up in ExpressPCB.
Hehe.
That’s the kicker, Mike.
I don’t make PCBs.
I just really like their schematic program.
It reminds me a lot of good old MSPaint.
I plan on cramming all of this onto one 2.3" square perfboard.
The other 2.3" square perfboard will have the micro and all it’s junk on it.
Yes… it’ll be a bit tight.
I agree that ExpressPCB is the best schematic drawing program out there. I love the ease of use and the incredible quality when printed with a laser printer. The output of the schematic is press quality in my opinion. One can make beautiful PDF schematics.
You should try to make at least one PCB.
Go on Nick… Try it 
Linky no worky here either. 
Running video streams over windows remote desktop connection is just too slow. A proper video stream would work a lot better. I was referring to running the r/c car remotely over the net.
I am using RoboRealm but not for the real r/c drivng project. I am using it to get another pan/tilt base to track a red ball. It works pretty well, I was suprised on how easy it was to setup such a complex task. Later on when I get the driving project done I will make the car track the red ball and drive to it…sort of like robo fetch.
Fantastic! I plan to send the video feeds using a 2.4ghz transmitter.
SN96,
Sorry I wasnt being clear. The camera is a wireless camera that transmits video back to my PC. I was talking about running the car over the net instead of having to be at the PC the wireless video is comming into.
Anyway I thought it would be about time for a new video. I got the headtracking visor in a few days ago and I have been working to get the head tracking working. It is a little rough and needs to be set up a lot but it can give you an idea of what Im going for. Since I know everyone can see flash videos I put it up on youtube: youtube.com/watch?v=4RfmbwsM7go
OMG! that is bad to the bone! How does it know its angle?
I can see an application for bipeds using this device.
Is this one yours too? It’s a PC racing wheel interfaced to an R/C car. Very cool! It would be even more cool along with the head tracking goggles - it would truely give you that “really being there” feeling.
8-Dale
