January 2008 Summary

Here’s a summary of work and posts for January

Posted by Chris on January 31st, 2008 in Update | No Comments


Updated Charging Circuit

Update 4/21/08: Click here for the latest wiring schematic.

A few weeks ago, I’d posted my simple charging schematic that I’ve implemented in my Artoo. It allows me to switch between normal usage or battery charging. I’m not an electrical engineer by any stretch of the imagination, and my wiring diagram wasn’t very elegant, but the setup worked fine.

Bob Ross pointed out that I really didn’t need to isolate the ground connections in the system while charging. This would save me one relay, and power to run it. He was kind enough to redraw the simplified circuit for me, and also came up with an improved design which allows me to run my droid (low load systems) from an external 12VDC power supply while the batteries charge.

Now that I have my new 60A relays I’m hoping to wire this up over the weekend, but thought I’d share it here first.

[PDF Version]

Thanks again Bob :)

Posted by Chris on January 24th, 2008 in Electronics | 3 Comments

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Relays for Charging System

I’m using simple 12V SPDT automotive relays in my droid to control switching of power between normal operation and the charging system.

Typically automotive relays are 30A/40A, but I felt I needed something a little bit more substantial. I found these 60/80A relays at SkyCraft for less than $5, which is very reasonable. I’d tried to find something local but came up blank.

The only catch is the terminals are 3/8″, instead of the more normal 1/4″, luckily I found some at Pep Boys for a couple of bucks. I’m hoping to work on getting my electronics re-installed this week and i’ll swap these into my setup at the same time.

Posted by Chris on January 23rd, 2008 in Electronics | 1 Comment

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Skin and Skirt Fitting

I finally got around to fitting my newly painted skirt and skins to the frame. Overall I’m happy how they came out and can’t wait to get the panels fitted.

For some strange reason there’s now a gap where the skirt meets the bottom of the frame which wasn’t there before. I’m not sure if it’s something I can fix easily or if I’ll even notice once I get him back on 3 legs.

I still need to glue on the small panels with silicon, but that should be relatively easy. For the larger panels I’ll probably use silicon too, but I’m hoping to hinge some of the front one’s.

Now that the skins are on I could mark the holes on the frame rings for adjustable brackets that hold things like the octagon ports and power couplers in place.

Posted by Chris on January 23rd, 2008 in Body | No Comments

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My Lost C4 Interview

I vaguley remember doing a few interviews at C4, but never thought I’d see any of them. But today I found one on Youtube.

Posted by Chris on January 19th, 2008 in Events | No Comments

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Re-painting Skins Part 4

I think I’m done painting the skins. No really, I’m done! Why don’t you believe me?

I even started to peel away the masking tape, so there’s no going back – Okay, okay. I know I’ve done this before but I mean it this time.

But seriously, I’m much happier with the finish now and can’t see me going back to do this again anytime soon.

There’s a few spot on the inner skin I need to clean up but it should be easy. It’s mostly the green undercoat that’s super thin and leaks under the masking tape easily.

Some bad news though – the top corner of the back door started to de-laminate once I’d removed the masking tape. The surface area for the glue isn’t very wide in this spot and I guess the epoxy was thin or non-existent. Once I get the panel inserts in place and epoxied, it should be an easy fix it without marking the paint.

I couldn’t resist laying some of the panelssee how things would look. Hopefully this week I’ll get some hinges working, and the permantent panels/inserts epoxied in to the skins.

I do need to clean up the epoxy on some inside edges of the panels as they’re not sitting exactly square, but overall I’m happy how things came out

I also went back and started to remove the tape and latex on the horse shoes. I scored the perimeter with a knife to help get a cleaner line

Next up, gluing all those panels in place and fitting the back door.

Posted by Chris on January 13th, 2008 in General | No Comments

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Periscope Port Detail

Here’s something else I’d forgotten I’d worked on before C4 and not posted.

The original dome periscope had a small raised lip around the side ports/windows. Neither my PVC or aluminum periscope kit has this so I improvised.

I used a 1″ Nylon gasket from the plumbing department at my local Ace Hardware store, and just superglued it in place. However, paint has a real hard time adhering to Nylon, so if I was to do this again I’d probably try and find an O ring made from something different. Also if you try and rough up it up you’ll get fine strands that will never go away.

I guess I’m posting this as an idea rather than a solution.

Posted by Chris on January 11th, 2008 in Dome | 1 Comment

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Periscope LEDs and RoboteQ

Not a whole lot going on. I did find a very cool surplus electronics store this week in Santa Clara called HSC. They carry a LOT of stuff at a fraction of the cost and the place is full of things that can be used on R2. I was hoping to find a slip ring to experiment with but I was out of luck. I did pick up a few bits though, including some red rectangular LEDs for the front slot on the periscope.

I did a quick test fitting on my aluminum periscope housing and they fit perfectly.

There’s very little published reference material for the periscope, but I have it on good authority that the front red light was made up of 6 of these LEDs.

I also worked a bit on my RoboteQ speed controller, adding a RS232 connection to the provided PWM cable to allow me to monitor things live from a tethered laptop. Basically I ran two wires (RxD/GND) from the 25-pin plug they provide to a 9-pin RS232 plug/housing.

The plug you see on the right may look like an RS232 connector, but it’s really used to connect just two PWM wires from the Vex receiver into the RoboteQ. It comes as standard with the controller, and they also provide a seperate RS232 cable to connect your computer. I really don’t understand why they don’t just provide one combine cable. Confused? Please see the RoboteQ manuals :)

Once the controller is connect to my computer I can use they’re monitoring software called roborun. It polls the speed controller and graphs live data like battery voltage, controller temperature, current being used, PWM data etc. It also allows me to exercise the motors without using my RC transmitter.

Posted by Chris on January 10th, 2008 in Electronics | 2 Comments

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