Robosapien RF Sound Mod


The purpose of this page is to house my ongoing development blog for a modified sound system for a Robosapien robot. The majority of these entries were originally made in this thread in the forums at The original concept was to use the RF receiver from a set of wireless headphones so that Robosapien could play .mp3 music files, and for that matter any sound from my PC. This ties in nicely with the PC control scheme I designed for Robosapien.

Questions or comments? Email me


Entry #1 -- August 9, 2004

I gutted a set of Emerson EHP1000 wireless (RF) headphones I got for cheap on eBay. For now I just stuck the circuit board in the little slot behind Robosapien's head I did not want to make a more permanent decision until I can install a camera. This allows me to transmit sounds played on my PC to the Robosapien speaker. This works great with the PC Control setup I have, since MainLobby lets you assign multiple events to each control button. So I can press one button in the MainLobby GUI and it will send an IR command to Robosapien and also play a .mp3 file. With the wireless setup it plays this sound through Robosapien's speaker. Robosapien now says whatever .mp3 I send to him, can play music, etc. The possibilities are interesting -- one could set up seperate control schemes for Robosapien with seperate sounds. Like 'football robosapien' -- programmed to dance and play the fight song of your favorite team, cuss at the refs, cheer for individual players, whatever you want -- with a custom themed GUI created in MainLobby. The problem seems to be a lack of amplification. I am a total newbie when it comes to electronics, so when I hooked this up, I basically just plugged in the RF transmitter into my headphone jack on my PC speakers and hooked up the Robosapien speaker to the wires that were used to hook up one of the headphone speakers. It's adequate volume through the Robosapien speaker (slightly lower than the default Robosapien voice), if I have the volume turned all the way up on my PC.

Here are the headphones I sacrificed:

Here are some pictures of the circuit board from the headphones, and my initial set up:

Here's the battery box I hotglued on Robosapien. I also drilled a hole for the power wires to enter his shell:

Temporary solution:



Entry #2 -- August 16, 2004

Well, the primary problem with the set up as it is, besides the form factor, is the lack of amplification. I've added a one watt amplifier, which works llike a charm. It was a nice easy 'intro to electronics' project for someone like me whose only experience soldering has been on electric guitars. I admit to buying and completing a 'Learn to Solder' kit from the same outfit prior to building the amp. So now I have more than enough volume, I realize how crap the speaker is. I also need a project box to pack in all the components, so I may as well look into replacing the speaker (maybe go hifi with a stereo setup?). Anyway, here are some pictures:

Next steps are to enclose all the boards and batteries, and upgrade the speaker.



Entry #3 -- August 19, 2004

Just an update: The RF system is working great with the added amplifier. Except the RS speaker sounded like crap trying to play music through it. The solution may be in a set of 10 year old unamplified Sony Walkman speakers I had laying around. The speakers in them are each 8 ohm and 0.2 watts, so I wired them in series -- the sound is much much improved. The problem is that the speakers are pretty big at 2.5" and 3/4" thick, plus I now have a 9v battery and two 'AAA' batteries in the mix, plus the amplifier pcb and the RF headset pcb. Obviously I am going to have to house all this hardware in some sort of a backpack/project box.

Once I decided that I needed to house all of the RF equipment and improved speakers 'off site' of Robosapien, I wired up a toggle switch on the robot's back that turns off his internal speaker. I found I was missing his 'caveman talk' -- which I found quite strange. I ran a set of wires out of Robosapien to hook up his internal sounds with the external set up, although I am not really sure they are needed. I left them because I figure any backpack arrangement will end up blocking his internal speaker.

Building the project box seems to be the issue at this point. All of the boxes at Radio Shack were either too big or too small. I first tried a plastic box that housed a set of hobby knives, with the original speaker grills. I liked the size but it was too shallow for all the boards and batteries. On a whim I next tried a tin Illy espresso pod box. Too big, just too much empty space.

So for now I am trying to sort out some sort of an enclosure.

Here's the mini toggle on-off switch for Robosapien's native speaker:

Here is the first prototype for his speaker backpack. The blue box is from a cheapo hobby knife kit that I cut out -- the grilles are dremeled out from the original Sony speakers.

Here's the latest -- an Illy espresso pod tin, ha ha. Note the holes in the side which hold the speakers, the battery holders in the floor and the hole in the front for the volume pot. Way too much empty space in there though. I guess I need to custom make something.



Entry #4 -- August 28, 2004

Some more updates. I don't know if I will ever finish this project. Anyway, I was at Radio Shack trying to figure out some sort of project box or something to hold all the stuff: speaker(s), amplifier, RF receiver, a 9V and two 'AAA'. I came across a decent little 'mini amplifier/speaker' -- it's a nice little package, about the size of a handheld transistor radio. Its 200 mW and drives a 16 ohm 0.5 watt speaker. Perfect robot backback. Using a couple of lids from the tin espresso boxes I rigged up an enclosure for the RF amplifier and the AA battery pack. I then velcroed it all together and to Robosapien's back. It's very secure on there and it works pretty well. I need to shield his upper body motors, they cause some interference.

Here's a couple shots of the backpack. In the second one you can see on Robosapien's left shoulder what happens when you accidentally set the shell down on a soldering iron, only to notice your mistake by the smell of burning plastic. The only decent flat mounting point on Robosapien was right on top of his speaker grille. I cut out the slots for more volume since the whole thing is now covered with velcro.

Here's the guts of the little amp. The pcb reminds me of a doughnut I may end up ditching that amp circuit and replacing it with a circuit based on a more powerful LM386 or a Philips TDA7052.

Here's what I rigged for the RF receiver circuit originally from the headphones.

I'm still not really very happy with this mod, although it works as intended, it's just ok.

The good: I've been having fun freaking out my dogs in the other room using a microphone and it would be great for tunes if the speakers were better. Once I install a camera it will add a nice dimension, especially if I can figure out how to control him via the internet.

The bad: The sound quality is subpar for music. The amp really isn't powerful enough. I still don't like the form factor too much and it sticks out pretty far on the robot's back. It's not really part of the robot. On one hand this is good, it is a very low-impact mod. Also a good intro to electronics/soldering project that won't fry your robot (as long as you don't set his shell down on your soldering iron.

Here's where I am heading:

- Cut out the robot's back and original speaker and try and do something about the form factor.
- Improve the amplifier using a circuit based on a LM386 or a Philips TDA7052.
- Improve the speakers and integrate it all onto the robot, so it's not a 'backpack' arrangement.



Entry #5 -- September 13, 2004

Since I am about to head out on vacation for a week, I wanted to give an update on the continuing work I have done on this project. I decided that the course of action I was going to take was to totally romove Robosapien's speaker and speaker enclosure. This was done with tin snips (ughh, I know) and a dremel. I took both pieces all the way down and now there is a good deal more room in his back shell:

I also ground down the little piece that is supposed to hold his speaker in place:

Looks like the awkwardly shaped PCB from the headphones will fit in the back shell nicely:

Here's what I had in mind for his new speaker system. The little radio shack amp I had used before as part of the backpack is also in the picture. The Sony set up was a cheapo find on eBay.

My main problem at this point is that although the Sony speaker set is amplified, it has no volume control and it just wasn't loud enough. I experimented with several little amplifiers that would control volume, including a nice little stereo 1w amp circuit I built based on a Phillips TDA7053A IC:

This setup is going to give me nightmares with form factor though. The next hurdle was turning the RF receiver circuit on and off. I set to dremel out a slot on robosapien's neck area so that I could use the thumbwheel on/off switch that was originally for the RF wireless headphones. I already had put a mini toggle switch here to turn off Robosapien's internal speaker earlier in this project. Unfortunately this was a mistake -- no matter how I tried, I could not get the thumbwheel to line up properly in the slot. I was having a few beers and I just kept making the slot bigger and bigger and bigger....

Oh well. I ended up using the mini toggle and adding an LED there to indicate when the RF circuit was turned on. I used several layers of Tamiya modelling putty to close up the gap I made. I still need to sand and paint it but here's how it turned out:

I added a little 1/8" jack -- mirror image to the spot where Robosapien's on/off switch is:

Here's the inside all put together:

So that's where it is. But still not done. Basically at this point I still need to decide on some sort of amplifier/volume control, and I need to hook back up Robosapiens 'voice' so it transmits through the external speaker.

Right now I have a stereo connection if I run directly from the RF receiver module, into the Phillips amp, and then into the Sony speaker system. The amp is very unweildy from a form factor perspective though, and there is no room for it in his shell. There might be in the chest if I didn't have the wireless camera in there.

What I am leaning towards at this point is using the Radio Shack 'backpack' amp/speaker and completely rebuilding it to pass through a stereo signal. So just basically use the Radio Shack amp as the main speaker system for when Robosapien is walking around, but provide the ability to hook up the much better-sounding Sony speakers if I want to. This solution is attractive too because the Sony system weighs about three times as much as the Radio Shack one. It is unattractive though because I would really like to integrate and use the much better looking and better sounding Sony speakers.

Hopefully I can come up with some ideas while on holiday.


Entry #6 -- October 18, 2004

Here's the latest update. The Sony speaker system sounds fantastic, and plays both the RF receiver input (in stereo) and Robosapien's native voice (mono). The project box contains the stereo amplifier built around the Phillips TDA7053A with volume control, some extremely simplistic mixer circuitry, the 9v for the amp and the 9v for the wireless camera. I added an on/off toggle and an indicator LED for the amp. The two cables running from Robosapien into the project box are for the mono voice and the stereo signal from the RF receiver. The two 'AAA' batteries for the RF reciever inside Robosapien''s shell are velcro-ed on his back.

Pretty much the coolest .mp3 boombox ever?

At this point, there are still a few loose ends that need to be tied down:

- I am using industrial strength Velcro to hold the speakers on Robosapien, and the project box on the speakers. It is pretty heavy. I will need to come up with a better solution to attach it, maybe bolts or pegs or some sort.

- The weight of the speaker system is such that it slows down Robosapien's walking speed. This isn't such a bad thing, as it helps to stabilize him and make the wireless camera feed less jittery.

- The amplifier eats through batteries pretty quickly.

- I need to make longer patch cables so that the entire 'backpack' can be removed once Robosapien reaches his destination. I made them a little too short.