What is inside a 35mm point&shoot camera

After few days in the hands of my daughter, a point and shoot 35mm camera plastic has started to break apart... time to put it aside and start opening it up.

It was a Minolta Riva Zoom Pico with a motorized 35-60mm zoom lens and autofocus. It did allow me to experiment with photography, and it took good pictures.

Anyway, I never opened up a photocamera, so I was curious to see what was inside.


I was surprised to find "enough" electronics, all mounted on a flexible PCB fit between the inner body and the outer shield. The electrolytic capacitor of the flash (220 uF, 300 V) was fit inside the film roll cylinder: a very smart arrangment. Everything was a tight fit and I bet it was hand assembled back in 1994 or so. What else can be taken off and recycled? Here's a list:

• flash strobe with circuitry
• small screws
• whitworth 1/4" nut (plastic)
• small plastic gears
  
• DC stepper motor
• lenses
• (zoom) objective
• photoresistor
• IR LED
• 200 pixel sensor from the autofocus
  

Out of all electronics in the list above, very little can be reused in other projects, the easiest probably being the flash strobe circuitry once the pinout is sorted out. On the PCB there are very few "useful" components.

The zoom objective has many wires making it almost impossible to control it from the outside (zoom, focus and shutter), so it is stuck in the "rest" position.

Lenses can be used to experiment with light.. maybe one of the small biconvex lenses from the autofocus could focus the Sun and set something on fire?!

Last but not least, around the camera body there are some metallic springy contacts that could become a Morse key.

LCD and contrast (HD44780)

I want to issue a word of caution about the contrast pin wiring on HD44780 compatible liquid crystal displays.

All my diagrams show the contrast pin going directly to ground: that's how my display works. Any voltage level higher than that makes the contrast too light and display unreadable.

Other displays need an intermediate voltage, so you better check out how yours works before soldering it in place! The datasheet might be a good starting point.


These displays will be used on my FT-817 Frequency Reader and Interactive Frequency Reader projects, so I will have to be careful too. ;-)

Cellphone remote control, just an idea

A very close family member has asked me how it would be possible to switch on (electric) heating in a remote location. Through a phone call, of course, I replied. Requirements are pretty simple: I would have to close a relay, maybe open it back.

The location has a landline, but I have not found useful references online on how to interface with it (is that considered a pre-Internet era technology?!). So, let's go mobile.

Take a cellphone that allows to customize the ring tone depending on the caller:

• associate a fixed tone sound to one calling number: this will be the "ON" triggering event;
• associate a different fixed tone sound to another calling number as "OFF" triggering event;
• associate a third, no-sound, ringtone to all other numbers (default).

So if you want to switch ON and OFF, you'll need two different numbers to originate the call, both with Caller-ID enabled. Not a big deal. You could even block all other incoming calls, if the phone allows it.

Next, build some simple hardware to detect those two tones and throw them into a simple set/reset system that drives the relay. Or make it with a microcontroller. The latter solution would allow some feedback on the relay state if the cellphone can be configured to auto-answer a call: let the circuit emit two different sounds depending on the relay state (or Morse code!). Maybe don't let it beep forever, so neighbors won't get annoyed.

Note that this "interface" can be arranged without harming a cellphone, because the audio coupling can occur over the air (yes, the location is quiet and empty).

Let me look for some sound recognition sample code for AVRs... :-)

The Joule-Doh night light

What do you get if you take a joule-thief and put it inside a play-doh can? A yellow "Joule-Doh" light! (or a "Play-Thief" one?!)


Recently I have re-engineered my homebuilt joule-thief after a too heavy shake that broke one wire. It was a good chance to let my older daughter choose for a new container, and a new color.

An empty play-doh can laying around was chosen as the new night light. The lid holds just right a 1xAA container and a small SPST slide-switch. Wires hold up the LED.


The 5mm while LED gives a quite directional light beam, but the transparentish can allows the light to be diffused around.

The Joule-Doh night light generates enough brightness in a dark 4x5m room so that you can walk around without hitting abandoned toys and tuck your child(ren) up.

For those not familiar with the "Joule thief", it is an oscillating circuit that allows to light a LED out of a 1.5V battery (be it AA, AAA or button). It usually works down to 0.8V, so it is a very good way to drain all the juice from those batteries that won't work anymore in normal toys. This one has been running already for 5 nights off the same "officially discharged" AA battery.

TTL oscillator as NE602 external source

There are lazy moments in everyone's life when you want to drive the NE602 LO input with a TTL-generated signal. I had asked on the qrp-tech forum few months ago and got helpful replies.

NE602 datasheet reccommends a 200 to 300 mV p-p drive from an external LO.

An application note shows this arrangment with a resistive divider for a TTL signal: 510 and 30 ohm, fed through a 0.1uF capacitor. This results in 277 mVpp for a 0-5V square signal.

Simple, isn't it?

Since I ignore the output switng of the canned oscillator I intend to use, I will try with a 1k multiturn trimmer and tune for an acceptable level.

FT817 external display, video instructions (it)

Today I think that there is no better way than a video to show a product's features, and to get some feedback about it.

So I produced 5'30" worth of video-instructions for the external frequency readout for transverter users. The audio is in Italian and I will add English subtitles.



Current features were summarized in another post. Please send feedback via email.

External display for transverter, diagram

Here is the schematic diagram for the external display based on ATmega168 (or mega48 or mega88 or mega328). Click to enlarge:


The component count is as low as possible. You may choose to take the supply from another source than the FT8x7 ACC port, such as a dedicated 9V battery.

You cannot leave out the two N.O. pushbuttons "[Up]" and "[Enter]" ("[Next]" on the diagram), but you can skip the LCD backlight control (mind the total supply current does not exceed 100mA, better less!).

This circuit is also the base for the keypad+display device I am still working on. The keyboard extension chip (PCF8574) will be connected to pins 4-5-6, so leave room for it on your board... in case you'll be interested in that device too.

"Release Candidate 1" ("RC1") firmware is available on request, until I publish it on my website.

Testers needed.

FT817 external display, revised

The external display firmware for ATmega48/88/168 chips is ready for a public beta.

I have kept a two-button user control interface and changed the LO programming method.

Since the survey (and following emails) showed that it is possible to have 100 Hz accuracy on 47 GHz transverters (WOW!), the display now allows 0.1 kHz resolution both for LO and VFO.
The LO value, 16 values actually, are inserted digit-by-digit through the two buttons when in "config mode".

Updated characteristics are:

• based on ATmega48/88/168 chip clocked at 11.052 MHz
• 2*16 character display (HD44780)
• 2 buttons interaction
• "config" and "normal" operation modes
  
• 16 LO values stored in EEPROM (survive poweroff, can be fewer)
  
• LO value down to 100 Hz
• LO ranges from 0 to 214'748'364'700 Hz (that's 214.7 GHz)
• VFO/output frequency computed to 100 Hz resolution
• support for both Out= LO+IF and Out=LO-IF
• LO value selection by button press (1 > 2 > ... > 15 > 16 > 1 > ...)
• VFO A/B toggle on second button
  

The "config mode" is accessed at display powerup by pressing a button. Reboot the display to enter normal operation mode.

I am working on a circuit diagram to be published soon. Who built the ATtiny2313-based display can assemble a simple adapter board for ATmega chips.