It had a busy weekend, but I did find some time to work on R2. I decided to continue focusing on the sound system and electronics in general as it’s easier to start and stop with minimum mess and cleanup.

I did hear back from ACS about the specs on the internal amplifier in the CF3 sound system. It turns out I was right and it can deliver 25W per channel, or 50W total. Their manual is rather vague and states it can only do 20W total, so I’m glad I checked now. I bought some new generic 4 1/2″ 4 ohm 30W speakers to test and they sound pretty good and seem louder and clearer than the single 15W horn speak I was using. Each speaker is connected to it’s down channel and delivers more sound than my ears could handle comfortably. I’m probably going to mount them behind the front vents for now, but may end up moving one into the skirt to bounce some sound off the floor to help it travel further and in more directions.

With the speakers out of the way I started to think about how I had the electronics laid out. Some of you may remember this is what my original electronic mounting panel looked like for C4.

It’s worked great, but I need to add a few things and as it stands, once the skins go on, I think it will be hard to use the hinged electronics panel to get access to the internals of the droid for maintenance, e.g. the batteries. I’m thinking it maybe simpler to move some or all of it internally to the droid.

With that said I started to disassemble the rear panel. I needed to do it anyway to add the Contact 24 I/O daughter card to the CF3 sound system. This will give me more options on the range of sounds I can trigger.

I’d been putting this off for a while as everything was working okay, and I could sort of live with only being able to trigger two banks of random sound vs the possibility of twelve banks.

With the everything disassembled adding the daughter board to the CF3 was a snap.

While I had the CF3 open I wanted to add an external connector to the white 3 pin header which bring out the volume control. It’s located just below the new Contact 24 daughter board and next to the CF card slot. I plan on connecting it to 2 channels on an RF receiver/relay board to allow me to adjust volume remotely.

The plug is pretty standard and I ended up buying a $2 fan extension cable as I couldn’t find loose plugs locally.

But there was a slight problem, the plug is too long and stops you from putting the Contact 24 card back in it’s place so I had to chop down the plug a bit.

I drilled a hole in the side of the box for the wire to pass through

I temporarily wired up the three contacts (up, down, common ground) to my RF receiver to try it out and it worked first time which surprised me. The plan is to have the volume on it’s own RF remote as I wanted to keep all 12 channels free on my original RF remote just to trigger sounds.

Now that the Contact 24 board was in place, I could start wiring up all 12 channels to the RF receiver using some hacked-up twisted pair LAN cable I had laying around.

Basically all the connectors labeled “A” on the RF receiver are connected to the adjacent “A” and then over to the common ground on the CF3 sound system. Then I connected the “B” connector of each relay over to a contact on the CF3. Starting at the top left going down is relay 1 thru 7, then on right starting at the bottom going up is relay 8 thru 12 . Each connections maps over to contacts 1-12 on the Contact Sense 24 board in the CF3.

This is the CF3/Contact Sense 24 side of the wiring. Each block of green plugs/connectors has 10 connections. The outside two are common ground. I’m only using one from each block and routing it over to the the two halves of the remote relay board (brown wire)

Here’s the the connections on the smaller 4 channel RF Receive from the CF3 volume cable. Note that on the 4 channel receiver we’re using connections B and C instead of A and B. This caught me of guard as the documentation that comes with the board is incorrect.

I’m going to Velcro each of the RF Receiver to the top of the CF3 case.

Right now I have the two RF remotes Velcro’d to the side of my transmitter, but I’m tempted to create a small box with better switches on it similar to the Vantec KeyCoder and have the RF transmitters hidden inside.

And finally here’s a wiring diagram I created that will hopefully make things a little easier to understand. There’s also a PDF version for printing.

Next step is to reprogram the CF memory card to use all 12 channels of the remote.

When out and about with R2 or when conversation turns to hobbies and invariable R2 building, it’s always handy to have a card ready with your contact information.

I’d created a simple business card design to use a Celebration 4, but I gave away my last one today, so I decided to create some new one’s tonight. What do you think?

Standard trading cards are a little larger than a business card so I may shrink them down to fit in my wallet easier.

[edit] Here’s the front and back of the new smaller business card next to the original larger trading card on top. I printed them on heavy card stock using my inkjet printer and they came out great.

I’m almost done with prepping the aluminum skirt.

With the olive paint and screws this pieces would looks more at home attached to the Nautilus or some Steampunk project don’t you think?

I’d bolted on the strips a few weeks ago and had given it a coat of primer, but I still needed to go back and file down down the  strips a bit.

I’ve also filled some of the seams with Bondo. All that’s left is to give it another shot of primer then it’ll be ready for the white top coat.

I’ve been busy the last few days and not had much time for building. I did get to work on the ankles and legs a little bit more and I think I’m pretty much done, minus one small piece that I need to buy something for to fix.

I’ve mentioned this before, but now that the ankles are back attached the to the feet it was hard to slip the battery boxes over the motors.

The right box went on no problem but I had to make a small adjustment to the left one one and open up the hole a tad. I also had to shave a little bit more off the top of one of the motors, to get the box to sit flush with the foot.

The boxes are really springy with the hoses attached and and there is no way the two screws that are supposed to push fit into the slots will hold the boxes flush to the feet. At least I couldn’t get it to work satisfactorily.

I think I’m going to have to come up with another method of securing the boxes, and will probably use some super strong magnets. That way I don’t need to fiddle with setting screws in tight spaces.

I ended the evening with attaching the legs to the ankles. I used pan head bolts, lock washers and fender washers instead of the countersink Phillips. This will hopefully give them more substance and grip on the legs. The 10-24 Phillips work their way loose way to easy even with thread lock glue, and I’ve had a few wiggle loose during a single outing and sheer off. If this fix doesn’t work I’ll knock out the 10-24 threaded inserts in the legs and use 1/4-20’s bolts instead.

I’m going to try and paint the bolts and washers white to hopefully hide them a bit.

That just leave the battery harnesses and back foot strips to silicon in place, and of course the magnets to hold the boxes.

I’m trying to resolve a lot of issues before I get to fully re-assembling my droid. It’s a real pain to pull him apart and I want to fix a bunch of things that have been bugging me like the slow dome. Another thing on my to-do list is the speaker.

I chose to use a 15W Horn Speaker on the recommendation of someone, and it does reproduce R2’s tinnie/metallic/middy sounds great. The price was right at the time too, but I think I can do better. It’s not as loud as some R2’s I’ve heard using in similar setups – which is my main motivation to find something different. The horn also takes a lot of space and I’m hoping to re-appropriate that for some electronics.

I’ve spend some time learning all about Ohms, Watts, Dbs and how they related to speakers and amplifiers. We’ve all heard the terms when we go out and buy the latest home theater surround system, but I never really understood what that meant in reality, e.g. you have 4 x 4 ohm 30Watts speakers and how that turns into how loud the speaker system is in Dbs.

Part of the problem deciding which new speaker(s) I should use is that the specs on the CF3 sound system I’m using from ACS are rather vague. They say the built in amplifier can deliver 20 Watts, but they don’t say if that’s across both channels, or if it’s per channel. And they don’t state how many Ohms the speaker should have.

With some digging I found that the sound board uses an AD 1994 chip, and here’s a summary of the specs

• 105 dB dynamic range
• 2 x 25 W output power (6 Ω)
• 1 x 50 W output power (3 Ω)

As you can see it’s rated at 50W for one channel or 25W on two. A lot more than the 20W than that ASC rates the CF3 system at. Also notice the 3 and 6 ohm for the speakers. Most speakers you find are either 4 or 8 ohm, maybe 16. Even if the amplifier can only do 20W, my current horn speaker falls short of taking advantage of that.

Tomorrow I’m going to call them up and ask some questions and report back.

Useful links –

• CF3 Manual and Data Sheet
• AD 1994 Chip Spec
• All about Ohms, Watts, Amps and Speakers

I’ve continued to do research and testing on my dome drive system, and it does look like I need to change the motor out for something with a bit more humph.

It seem that a few people are happy with driving the recommended GM9413 Pittman motor at 24V instead of 12V with good results, but I really want to avoid introducing the complexity of 24V into my system just for one motor. It will complicate charging the batteries at best and the shorten the system run time between charges, and at worse reduce the overall battery life unnecessarily.

In the last day or so I’ve got a lot of great advice from fellow builders, including a lot of links that helped me decide which new motor to go with. I wanted to stay with a Pittman if I could to hopefully avoid redesigning the dome drive system, and it looks like one of the variations of the Pittman GM9236 would work. It comes in a few different gearings and voltage ratings.

There was one specific 12V version I was shopping around for, the GM2936S018, which delivers about 3 times the torque, and about twice the RPMs of my current motor, but it was around $130, and I’d rather find something a little cheaper if I could. Then Bob pointed me at another GM9236 model that was very similar, but only $23 at a surplus store. They’re used/surplus but probably worth the risk so I ordered one to try. It has very similar specs delivering a lot more torque and hopefully went it’s installed, spin the dome a little faster 🙂

So here’s the links I used for my research and where to find motors

• Pittman website – not very good if want to look up older models, and you need to register to download specs.
• Skycraft Surplus – carries a lot of surplus motors, and right now has the GM9236 in stock.
• Skycraft’s Pittman Motor Guide
• Click Automation’s Pittman Spec and Price List– good overview and side by side comparison of a lot of the Pittman’s out there.

It does look like I may end up trying running the Pittman Dome Motor at 24 volts as a test going forward. I can’t see adding a gear at this point in time.

This leads me to my next problem, my battery sub-system is all 12 volts. I’ve had no need for 24 volts in the body as my main drive motors the NPC-2212’s can only run at 12 volts, and everything else is stepped down from 12 volts using Dan’s distribution board.

I know how easy it is to create 24 volts from two 12 volt batteries, which I have and can do with what I have on hand, but configuring in series and then tapping off for 12 volts adds a level of complexity for charging the batteries w/o removing or rewiring each time. There’s also the problem of one battery draining faster.

For those unfamiliar with creating 24 volt from 12 volt batteries, this is a really good site explaining how and some of the problems.

One of the problems he talks about is charging unbalanced batteries in parallel and something called a “Battery Equalizers / Balancers” which can fix this problem. The unbalance comes from the 12 volt tap on a 24 volt system, and the two batteries discharging at different rates.

I’m hoping someone has tried an equalizer in their droid before. I’ve found a lot of information on equalizers, mostly large clunky boxes for RV’s and buses, but there are smaller version out the like this one.

What I’m hoping is to use the 3 12 volt 7amp batteries I’m using right now in parallel, and then combine two of these in series for 24 volts. For charging have a switch/circuit to disconnect/isolate them from anything in the droid and reconfigure just in the parallel state to charge all 3 batteries together.

Tall order I know without causing a short circuit or fire 🙂

Okay, I promise this will be the last KHF post for a while. I bought a bunch of plugs from Ace and tried them out tonight and I think I’ve found a keeper.

It’s a small nylon plug that normally leafs out when a nail is pushed through, but I removed the nail and tapped the hole for a bolt.

I’m pretty sure it’ll hold for now, but would pull out if I gave it a really good tug. The good thing about this plug is that the expansion happens at the top in side the aluminum KHF holding it snug.

I also tried a small metal wall plug, but it didn’t work so well and deformed when expanded in such a tight space in the tube. I’d probably have to replace it every time I took the hoses off, it also didn’t grip the hose so well as the nylon one.