Anyone build a recharging station?

Lynxmotion
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Has anyone built a recharging station for there autonomous bot? A station were the bot can go and recharge the batteries all by himself.

1 Like
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I haven’t, but… What about the Roomba? It has a docking station, or something like, for power. It might be something to look at for inspiration, at least.

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Getting hold of a “Roomba” would be great but I have never seen one here in Greece.

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Can’t help too much with getting a Roomba, but here’s a picture of the docking station (or “home base” as they call it):

http://irbt.imageg.net/graphics/product_images/pIROBOT1-3960253dt.jpg

Not too much information there, but here’s a link to the page the picture came from.

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Hi All,

I have several of the iRobot docking stations and I believe that they do not contain charging circuitry. They just supply around +22vdc to the Robot through the charging pads in the base.

I believe that the charging circuitry in the Robot uses the +22vdc to charge the onboard 14.4 vdc battery. The charger in the Robot monitors both the battery voltage and temperature to maintain the highest charging rate without damaging the battery.

You could use a Vellmen NiCad/NMHi battery charger kit (not the charger/discharger kit) as an onboard battery charger and limit the charging current to 1/10 C so that there would be no need to monitor battery voltage or temperature. The charge rate would be slow, but you would not have to worry about overcharging the battery and the battery would be in a float condition after being charged.

You will have to provide some circuitry to sense when the Robot is docked and switch over to the charging mode.

Just a thought.

Regards,
TCIII

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This is also on my list of things to do with my Rover project as well. It would be nice to build some thing like the iRobot station that outputs some signal (ir?) that a sensor or sensors on the rover could use to locate it. Maybe on the bottom of the rover or maybe the back of the rover have a couple of contacts to connect to the charging station and maybe one or two other contacts to get/give some feedback information.

I was thinking about hacking up one of the Universal Smart Chargers (7.2 to 12v) to have the smarts of the charging. The battery on board the rover is 12V and the electronics are being passed 6v through the adjustable HD Regulator lynxmotion.com/Product.aspx?productID=470&CategoryID=48. So I was thinking I might be able to have the processor continue to run while being charged? One problem of this approach would be knowing when the charging is complete. Maybe could hack up the charger to somehow know which LED is on…

It will probably be awhile before I get to this, so I will be interested to see what other approaches people come up with…

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The actual charger itself will no be a problem to construct. The real adventure is to make a reliable homing circuit that will guide the bot to the base all of the time.

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Just wanted to throw out an idea: How about inductive charging, like what Oral-B uses to charge their electric tootbrushes? It’s inductive charging so there is no metal to metal contact, so there is no chance of oxidation/corrosion, and you don’t have to be too precise, just have to be around that area…

Just a thought… :slight_smile:

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The Roomba stuff does use IR for homing in. In fact, if you browse the inventor portion of their site, I remember seeing a white paper on it (look at their white papers for the Create platform).

Inductive charging would be bad for robots I think, as it would cause all sorts of RF at the microprocessor level. I have some of those candles that charge inductively, and they not only take forever to charge, but also require three foot clearance from other electronics (or so the manual says).

— Edit —

Ok, slightly mispoke. There are far less details then I remembered.
On page 18 of the Create Open Interface it shows that the iRobot base station emits three fields of IR, based on distance, and offset location.

If we were to do this homebrew, I imagine we could do the same thing, with multiple frequencies of IR encoding.

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Really this is a question of proper design. Consider that the candle things you mention are a super mass produced consumer item that is as cheap as possible to build. More than likely to meet FCC compliance in the US they need the warning so that if you the consumer “choose” not follow their recommendation and experience interference then it is your responsibility to move stuff around and fix it. A custom charging base on the other hand can be built to close tolerances with magnetics tuned to your specific application. Probably the biggest thing you can do to help yourself is to minimize the air gap in the magnetic coupling. Alignment of the core between the base and the robot would be critical, possibly enough to warrant actively moving the part in the base in X-Y to get the optimum amount of energy across. Then I would look at operating the transformer you have constructed near its resonant frequency so it takes the least amount of power, meaing you get more power to the robot for the same power input. If you drive the circuit with a clean sinewave in a sub-MHz frequency range then you should have no problems with inducing energy in places you don’t want it to be.