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.

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 🙂

Tonight I’ve started to work on some dome stuff, including the dome drive system which has been bugging me for months.

I’m using Darren’s dome drive kit (based on Atomic Pickle’s) and it uses the Pittman GM9413-2 geared motor. Spec’d at 12v, 19.7:1, 142RPM.

To me it seems sluggish and rotates slowly compared to a lot of other droids I’ve seen, especially when I change direction. It could be the weight of the dome, which is around 17lb with all the accessories. Including all alu parts, like HP’s, surrounds, radar eye, dome ring, and periscope, plus the batteries, smoke/fire-extinguisher etc. etc. But I’m sure I’m not the only one with a heavy dome.

I’m wondering if others are experiences sluggish domes who are using this Pittman either from Darren’s kit or from AP’s? Especially if your dome is heavy?

According to the GM9413-2 data sheet on the AP site, the motor is rated at 12v, which is what I’ve been running it at, but on the motor itself the label says 12/24v.

I’d rather not run it as 24v if I can help it – but if it would help I could re-configure some of my batteries as a last resort.

The only other thing I can think of is the slight sagging in the mounting, but the motor is making full contact with the rockler bearing. Maybe it’s not doing a great job of holding on or maybe pushing too hard against the rockler bearing?

I know many Sennaites are using the Saturn motors at 24v for the dome, but I’d rather not switch class of motors right now. I’ve posted to the Yahoo! Group to see if anyone has some suggestions specific to the Pittman motors.

Edited to add some videos. Here’s the Pittman running at 12v directly off a battery, no speed controller so startup is instant and it looks okay right now which I don’t understand. I’m wondering if it’s a speed controller issue, or maybe even a problem when he’s angled in 3 legged mode. mmm.

And here it is running at 24v – super fast I know, but I’d rather the top speed be fast and I can slow it down with the transmitter/speed controller commands.

Now to troubleshoot why the 12v spin seems okay.

I did some further testing tonight, and held the body at an angle while the dome spun. Man, is there a lot of force whipping around while it turns, even at the slower 12v. I can feel it struggle on the up swing as the two heavier side of the dome comes around. 24v helped a lot but I need to go back and put the speed controller back in the loop to confirm my test and see how snappy it is looking left and right.

There was some discussion on the builders message board recently about reprogramming the unique encoding on the newer 12 channel RF remotes.

Much of the documentation and notes on various R2 sites are for the older remotes. I thought it might be a good idea to document my findings on the new remotes.

I don’t want to repeat in detail why or how R2 builders use these boards, but the most common is to trigger sounds in your droid when combined with a CF3 sound system. Most of what’s been written about integrating the board into your droid applies no matter which revision you have – but changing the encoding has.

First up, most people find these boards on ebay. Just search on “12 rf remote” and you’ll find a lot of sellers offering them from all over the world. Don’t pay more than $30-40 with shipping. There’s still a few sellers offering the older boards too.

So what’s the difference between them? Not a lot to be honest. The newer boards are easier to reprogram the unique identifying code, and the transmitter is a little smaller. However the new receiver board does have an annoying buzzer that needs disabling.

For the geek in you – On the receiver board, auto learning decoding scheme has been programmed into the MCU IC chip, and inside the remote control or transmitter there’s an Encoding IC Chip, an SC-2262. This set of IC chips can be used to encode your signals so that multiple remotes in close proximity will not interfere with each other. In theory you can pick from 6561 different combinations.

Do you need to worry about changing the code? That’s easy, most boards are shipped with the same factory default code, and you don’t want your droid to clash with some else’s.

For reference, here’s the older board and the remote which is somewhat larger

If you have one of these then jump over to Alex’s original RF remote tutorial.

Warning: The Positive/Negative terminals are swapped on the new and old boards. Please double check everything you’re doing with the latest wiring diagrams from the manufacturer. Don’t assume this tutorial is up to date.

And, here’s the new RF remote/receiver – notice the circle/tab toward the back of the board. That’s the buzzer. If yours has one of these then you have the newer board.

Unlike the older board, to change the unique encoding all you have to do is set it on the remote transmitter and then set the receiver to auto-learn mode, with a press of a button and you’re done. Well that’s the overly simplified explanation.

Here’s an overview of the receiver board with the location of the learn button marked at the bottom left.

Procedure to Learn and Erase Codes

• Press the “Learn” button on the receiver board, the siren will beep indicating the receiver is ready and waiting to learn from transmitter.
• Press any designated keys to teach and select Output modes. (See list below)
• If you need to reset/erase the the receiver due to lost or new remote, press “Learn” button for ~10sec until the siren beeps 3 times, which indicates previous learned codes have been erased.

Output Mode selection

Press 3 for Momentary Mode
Press 6 for Latched Mode
Press 9 for Toggle Mode
Press 12 for Ch1-Ch6: Toggle Mode, Ch7-Ch12: Momentary Mode

To set the encoding, first open up the transmitter

The chip at the bottom labeled SC-2262 is what does all the work.

Remove one more screw and separate the green circuit board from the casing

Notice the 3 rows of 8 little solder tabs at the bottom. That’s where you set the unique code using a soldering iron (one of 6561 or 3×8 combinations.)

Pin 1 through 8 bring out the Encode function of your remote transmitter. The receiver board will automatically learn from the transmitter by pressing the learn button.

On the older boards they used to labels the back of the board with a “H” for High, “L” for Low and numbers of the pin outs. Unfortunately the newer boards don’t have this luxury. I’ve marked up a photo to show the pin outs.

Low or ” L” – Low digital state (Close to GND level).
High or ” H” – High digital state (9-12V).

You should also be able to figure out the “L” and “H” states yourself. After you connect the system to power, use a Voltmeter to measure the contacts on both sides of the column of eight pins (1-8). Voltage level on each side should be consistence. If one side is “H”, the other side should be “L”. “H” level voltage can be measured only when signal is transmitting/receiving. Or simply use the above photo as reference.

Also, you don’t have to connect all eight pins to High or Low, just one will do. In my case pins 3 and 4 are connected to Low, and 7 to High.

Often remotes are default encoded to be 00000001, i.e. pin 8 is shorted to GND.

Encoded IC has following representation:

If the pin is not shorted to anything, its code value is “0”.
If the pin is shorted to Low, its code value is “1”,
If the pin is shorted to High, its code value is a “2”.

A couple of useful sites

• Light Object – they sell on ebay under the name of coldfusionx, are based in the USA and a lot of R2 builders buy their boards from them. This link has a bunch of support documentation on it.
• R2-R9.com – Jerry Green’s write up on integrating the remote with a CF2 sound system.
• AlexKung1.com – Alex’s original RF remote write-up.

Warning: I’ve just been informed that the Positive/Negative terminals are swapped on the new and old boards. Please double check everything you’re doing with the latest wiring diagrams from the manufacturer. Don’t assume this tutorial is up to date.

For those of you following along from the start you’ll know that I’m using the Vex System to control my droid.

Vex was originally a joint venture between IFI Robotics and RadioShack, but they parted ways back in 2006 and IFI took full control of the Vex Labs company.

Recently Vex Labs introduced the second generation Vex system called Vexplorer. On the surface it’s a simpler (and cheaper) design, but does have some cool things in the starter kit like a 2.4 GHz remote camera. The remote transmitter is a lot smaller too, more like a game controller.

It maybe worth checking out if you’re shopping around for a programmable micro-controller to run your droid.

Looks like the micro-controller is NOT programmable. So I can’t see this being much use beyond using it as a standard RC setup.  VexLabs has dubbed the new controller Vex-Blue vs Vex-Red for the original system I use.

I’ve come to the conclusion that external dome bump switches are a bad idea, for events at least.

I like the convenience of being able to quickly turn off the dome lights to save the battery, but kids quickly work out what they do and are constantly playing with them. They can’t do much damage but i’s very annoying, and I’m leaning toward replacing them with an internal switch even though it’ll be a pain to get at. I’m not sure if I’d leave the dead switches in place or replace them with simple bumps.

If you’re about to go down this route I’d personally recommend against having external switches of any kind.