ASSEMBLY
Once all the parts have arrived, assembly is fast and easy (relatively speaking) and is generally a great deal of fun. I’ll spare you all the pictures I took as most can be found elsewhere on this site, but one thing definitely requires mentioning:
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Shiny!
Also, I’m adding the a-style gripper:
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Assembly is smooth, without problems and completed after a few days.
WIRING
Now it gets interesting. Because of my rather long list of demands, I quickly decide I won’t be able to cram all the needed wires in the two screw terminals so I slap together a terminal block. This turns out to be an excellent idea because after a while, even my terminal block starts getting rather full.
Initial hookup is simple: BotboardII, the sabretooth motor controller, my connector block, and the supplied connectors and wires are all slapped together and from the first try, everything lights up as it should.
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Without putting everything together, I hook the arm servo’s up to the botboard, and quickly realise it’s not doing what it should: the arm jerks around a bit and dies, remaining motionless.
Some quick checks reveal that my cheaply acquired chinese 6V power supply can’t cope with the power demand. In fact, it’s a good half an amp below what it’s supposed to be able to deliver. I hook the (still uncharged!) batteries up and the whole thing does as it should.
I then wire the power pin connectors so, that when you plug in a power source, the batteries get disconnected. Unplugging switches back to battery power. I’ve added a capacitor to buffer the power supply, but this one still needs some beefing up as the botboard still resets. So if you want to hook the robot up to AC, all you need to do is plug the power in. Simple! It doesn’t even matter wether or not the battery switches are on or off, just plug in and play.
The next step makes wiring a bit complicated. Think “Docking station-” I want to be able to just drive the robot up against some contacts and the batteries charge. Also, I want to be able to leave the robot there indefinitely without me being around to turn anything off, or use the fire extinguisher, so the chargers need to switch off at some point. In addition to that, I want to be able to just drive the robot off again without any human interaction.
Now there’s several different ways of doing this, but I had to choose one, so I went with two smartchargers (cheaply acquired chinese ones, but after delivery they actually appear to be quite high quality). The robot will be fitted with a yet to be designed docking port, and a power relay.
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I still need to find a free drawing program that allows me to show you guys my scematics, but I’ll try to explain in short:
With the relay unpowered, the batteries (6 and 12V) feed my connector block.
I installed a small battleswitch to power the relay (which apparently draws 5mA more than the board can supply, damn!) and use a button to power it. I COULD simply leave out the relay and use two battleswitches instead, but the relay is a good deal cheaper and heavier duty.
Once powered, it completely disconnects the battery from the electronics and wires them to the docking port instead. Also, one wire from the docking port supplies 6V to the electronics, so everything still keeps running.
In other words: I have 4 wires going to the docking port. 6V, common, and one charge wire from each battery.
So when running on battery power, you drive up to the dock. 6V is transferred through the buffer diode. You check everything is in order (using the to be installed camera) and hit the charge button. The relay flicks over, batteries are now connected to the chargers and you can still happily move around the arm and camera.
This is definitely not the simplest or cheapest way of doing it, but considering the goal is to have the robot running without human presence, it’s the safest way of doing it. If anything goes wrong, the relay switches off, disconnects the chargers and resets the robot. If all goes right, the chargers switch to low trickle charge once the batteries are full, and the robot can stay there indefinitely.
I took a picture of the unassembled wiring, without any of the servo wires.
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As you might notice, I’m losing considerable space using bulky connectors, but I’m trying to keep most of the originally attached wiring intact. I could possibly gain some room by cutting them short and to size but I figured I’d want to wait with that until everything’s in the right spot and I actually run out of space.
