The New $15 Picaxe Talking Skull Controller

[halstaff]

I received the 5V power supply to run the wiper motor for the Kiwi controller board for the seance room and it works perfectly. All the components are happy and working together now.
The Kiwi board controls the entire scene. When the PIR is triggered, it starts a wiper motor on the rocking chair, starts the moving books, turns on the LED lights on both the books and the rocking chair, triggers the Tenda board to start and runs the jaw servo on the skeleton. After the skeleton says his piece, the audio, the rocking chair and its light stop. A second servo pushes down on the DVD remote and starts the Madame Leota projection. After it finishes, the moving books and its lights go off and the system waits for 60 seconds before it can be retriggered.
Everything including the PIR, Tenda board, Kiwi board, components, speakers and power supplies came to around $80 with the 5A power supplies costing $30 alone. I have to order some off Ebay to cut down that cost.
I'm posting it here instead of in its own thread as the few people interested seem to be following this thread.

[Dead Things]

Originally Posted by halstaff

I've finally got the Tenda boards to play nice with the servos for my talking skulls. Best single piece of advice I can give is to use a separate power source for the Tenda boards. After many frustrating hours spent, it was found that this was the biggest cause of problems we thought were due to programming.

Seperate power supply? Do tell. I want to use a computer power supply to run my prop, using the 5V rail to power the picaxe, servos and tenda. Am I asking too much of it?

[halstaff]

Using a computer power supply is certainly something I'm thinking of trying.
I have a 12V power supply coming into the Kiwi board with one rail running the 12V components except the wiper motor which has a separate 5V power supply. The Kiwi board has a 5V regulator to get the power for the Picaxe, PIR, LED eyes and the 2 servos. I tried running the wiper motor from the Kiwi board power but it was too big a load.
The audio/servo board with the Tenda player requires a separate power supply to eliminate interference.

[fritz42_male]

Hi Steve,

I've been reading up on the use of decoupling (bypass) capacitors and I think your trouble could be alleviated by putting a lot more decoupling on both boards. It's certainly worth a try.

Try a combo of 47nF Ceramic and 47uF/10V across the power lines as close to the chips as possible - a pair per chip and another pair on the power lines by the Tenda board

If it works then you can run on 1 5V supply for both boards.

[pshort]

If you have access to an oscilloscope, it might be interesting to see what the power pins on the PICAXE and the Tenda board look like. I'm working on a project with the Tenda board, powering it from a 9V battery (no servos running at the moment). I've noticed that there are some interesting glitches on the power input pins to the Tenda board when it's playing a clip. These pulses are about 100mV, last around 2.5 mS, and occur at random intervals on the order of 50-100 mS. Assuming that the output impedance of the battery is around 2Ω, this translates to about a 200 mA pulse, suggesting perhaps some sort of SMPS.

Do you think that the Tenda board is interfering with the servos, or the opposite?

[fritz42_male]

I'd say the Tenda board is interfering as that was the consensus on the Picaxe forum but Servos will interfere as well.

Steve (Halstaff) doesn't yet have an Oscilloscope but I have a couple of small ones that I can use when I get some time Xprotolab - brilliant!) http://www.gabotronics.com/developme...-xprotolab.htm


I'm also about to try an iTouch based scope (uses a microphone link and a 1x /10x probe). Also got a USB soundcard on order to try a PC based scope that uses the mic input (I can fry a USB soundcard and not worry - they are less than $5 delivered)

[hpropman]

yes you can use the computer power supply to power the board. Fritz please let us know how that USB scope works out for you I was looking at one myself.

[Dead Things]

Originally Posted by hpropman

yes you can use the computer power supply to power the board. Fritz please let us know how that USB scope works out for you I was looking at one myself.

Will it be able to power all the components? Picaxe, Pololu micro maestro,Tenda, 3 vent motors and 5-6 servos. I might be asking a lot of the 5V rail.

[fritz42_male]

Originally Posted by hpropman

yes you can use the computer power supply to power the board. Fritz please let us know how that USB scope works out for you I was looking at one myself.

Will do. There are usb 2 channel scopes on ebay that are Ok - 5v max input or make your own resistor divider probe.

http://www.ebay.com/itm/2-Channel-PC...item335fd379b7

But I like the idea of using a sound card and a cheap probe to do it. Then the same idea for a spare iTouch I have.

[pshort]

The difficulty with the sound card scopes is that they won't go down to DC in frequency, as they are (usually?) capacitively coupled.