Engineer from Télécom Paris
Ph.D Thesis from UPMC

Network & Security IT - MI
Check news about my company

Motorized Camera controlled by the telephone

For some years, I lodge different pets at home (Cat, Chinchilla, Hamsters).

Each time I tried to phone one of them, I was unable to understand what he said : I tried but never succeeded in teaching any human language to them. So, I created this motorized Camera controlled by the telephone, in order to supervise them when I'm at my office.

The system is made of 3 parts:

  • 1- a private PBX based on Asterisk: this Linux PC is connected to the PSTN. When it receives a phone call, it converts DTMF signals to commands sent into an asynchronous V.24 interface (RS-232-C),
  • 2- an electronic box based on a micro-controller that receives commands from a V.24 interface and is able to drive a motor (stepper),
  • 3- an USB camera attached to the stepper, broadcasting to the Internet.

The command part of the box is based on a microcontroller (Microchip PIC16F876) connected to my personal PBX (PC running Asterisk) through a serial port (thanks to the well-known MAX232N, a +5V-powered RS-232 driver). The power part is made of a quadruple half-H driver (L293D from Texas Instruments) driven by 4 inverters packaged in a SN7416.
Here are the schematics:

command part

power part

camera part

stepper part

SN476 + L293D both from Texas Instruments

What about the software parts ?

- The assembler code for the PIC is available here.
- In your PBX dial plan (Asterisk configuration file extensions.conf), you need to add the left and right actions (in this example, press 7 and 8 to let the camera rotate left and right):
; stepper
exten => 7,1,System(/bin/
exten => 7,n,Goto(s,begin)
exten => 8,1,System(/bin/
exten => 8,n,Goto(s,begin)

- These shell scripts call /bin/stepper (see stepper.c).

Top Articles:

ImageElectronic design: driving a 60A relay with a micro-controller
Use this device to drive a 60 Ampere relay in order to power on/off dozens of computers at once.

Image"new_station" patch for hostapd
Improve 802.1X authentication on wired IEEE 802 media, with this patch for hostapd.

Copy, manipulate and erase raw data on your usb flash drive. Essential to really get privacy with your files.

ImageHidden VNC server
This patch for WinVNC 4 allows you to install a hidden VNC server : no more tray icon.

ImageRaccorder son réseau d'entreprise à l'Internet
A free book about networks. First published by Eyrolles in 1997, and under terms of Creative Commons in 2006.
© A. Fenyo - F. Le Guern - S. Tardieu

IP phone to analog phone interface circuit
At work, people usually do not get an analog phone line anymore since numeric or IP phones appeared. See how to connect your old analog device (modem, wireless DECT phone, Minitel) only using your IP phone to get the network access: read this.

Very low cost 20MHz signal generator for ham radio HF power amplifiers testing
Learn how to make a 20MHz HF signal generator using a few simple discrete analog components. Moreover, see how a 33 years old Tektronix oscilloscope gives better results than a numeric one bought recently. The whole story is here.

Split tunneling with Cisco
Enabling split tunneling with Cisco IPsec VPN Linux client software is always possible: read this.

Modelling IEEE Spanning Tree protocols using an UML Class Diagram
To really understand the dependencies between the many Spanning Tree protocols, I wrote an UML class diagram describing their relationships here.

Motorized camera controlled by the telephone
This project demonstrates how to drive a camera from the telephone line, any details here.

External Links:

ImageMy Former Web Site
Since 04/26/01, I maintain a web site named Since I made many updates recently, click here to access the original content, where old informations are kept. The photo is also from 2001 :-)

ImageAgnes' Web Site
Agnes, my wife, used to maintain a web server but she doesn't anymore. Thus, this pointer is disabled. However, you may contact her on LinkedIn.

ImageCanardou's Web Site
Canardou has always been for me a friend that really matters, helping me in every situation. According to informations currently available, Canardou could be affected by the H5N1 virus. So, for a few weeks, Public Health Bird Regulations have made me forbid Canardou to walk away from our appartement. Feel free to take news about him from his personal home page.

Private Links:

ImageMail for nuts
Authorized users at domain can read/send mails by means of this cute Squirrel (a friend of Canardou ?).