The hub for the external USB ports has been fitted here, with the two ports hardwired to the pads where once there were USB A sockets. This hub will also accommodate the wireless receiver for the mini keyboard & mouse, in the remaining port that will sit between the external USB ports.
In this gap between the ports is where the wireless receiver will sit for the keyboard & mouse, the pair of screws securing the external ports in the centre have been shortened to make more room.
For convenience, a pair of USB ports have been fitted to the wearable Pi, which open on the bottom of the unit. These will be hardwired into a 4-port USB hub which will also support the wireless adaptor for the mini-keyboard that is to be used with the device.
The two USB ports on the bottom of the casing.
The external connectors are also complete. The audio jack & second WiFi antenna port are fitted.
The audio is normally routed to the LCD display speaker, until a jack is plugged into the 3.5mm socket.
Here is the project I’m currently working on. A completely wearable computing platform based on the Raspberry Pi & the WiFi Pineapple.
Above can be seen the general overview of the current unit.
On the left:
On the right:
The WiFi, Pineapple & 3G all have external antenna connections for a better signal & the whole unit locks onto the belt with a pair of clips.
The Raspberry Pi is using the composite video output to the 7″ LCD I am using, running at a resolution of 640×480. This gives a decent amount of desktop space while retaining readability of the display.
The case itself is a Pelican 1050 hard case, with it’s rubber lining removed. The belt clips are also a custom addition.
Here are the connections to the main unit, on the left is the main power connector, supplying +5v & +12v DC. The plug on the right is an 8-pin connection that carries two channels of video, mono audio & +12v power to the display.
Currently the only antenna fitted is the 3G.
Closeup of the connections for power, audio & video. The toggle switch is redundant & will soon be replaced with a 3.5mm stereo jack for headphones, as an alternative to the mono audio built into the display.
Current state of test. Here the unit is running, provided with an internet connection through the Pineapple’s 3G radio, funneled into the Pi via it’s ethernet connection.
Running on a car reversing camera monitor at 640×480 resolution. This works fairly well for the size of the monitor & the text is still large enough to be readable.
Stay tuned for Part 2 where I will build the power supply unit.
This is a late 90’s business timeclock, used for maintaining records of staff working times, by printing the time when used on a sheet of card.
Here is the top cover removed, which is normally locked in place to stop tampering. The unit is programmed with the 3 buttons & the row of DIP switches along the top edge.
Closeup of the settings panel, with all the various DIP switch options.
Cover plate removed from the top, showing the LCD & CPU board, the backup battery normally fits behind this. The CPU is a 4-bit microcontroller from NEC, with built in LCD driver.
Power Supply & prinhead drivers. This board is fitted with several NPN Darlington transistor arrays for driving the dox matrix printhead.
Printhead assembly itself. The print ribbon fits over the top of the head & over the pins at the bottom. The drive hammers & solenoids are housed in the circular top of the unit.
Bottom of the print head showing the row of impact pins used to create the printout.
Bottom of the solenoid assembly with the ribbon cable for power. There are 9 solenoids, to operate the 9 pins in the head.
Top layer of the printhead assembly, showing the leaf spring used to hold the hammers in the correct positions.
Hammer assembly. The fingers on the ends of the arms push on the pins to strike through the ribbon onto the card.
The ring of solenoids at the centre of the assembly. These are driven with 3A darlington power arrays on the PSU board.
There is only a single drive motor in the entire unit, that both clamps the card for printing & moves the printhead laterally across the card. Through a rack & pinion this also advances the ribbon with each print.
In preparation for my laser scanner project, I have modified my existing 445nm laser to accept a TTL blanking input. The laser driver is already enabled for this & just required an extra connection to interface with my laser scanner showboard. I have used an 8-pin connection to allow the same cable & interface to be used with an RGB laser system, when it arrives. The signals are as follows, from top centre, anti-clockwise:
Pin 1: +12v Power
Pin 2: Blue TTL
Pin3: GND
Pin 4: Green TTL
Pin 5: GND
Pin 6: Red TTL
Pin 7: GND
Centre: Power GND
Here is the custom 8 core cable, which connects to the laser scanner show board. This cable allows the laser to be used for projection while still retaining the portable function & the keylock arming switch. When plugged in the cable bypasses the keyswitch & provides 12v DC direct to the laser driver.
Having had a He-Ne laser tube for a while & the required power supply, it was time to mount the tube in a more sturdy manner. Above the tube is mounted with a pair of 32mm Terry Clips, with the power leads passing through the plastic top. The ballast resistor is built into the silicone rubber on the anode end of the tube. (Right).
Output power is about 1mW for this tube, which came from a supermarket barcode scanner from the 90’s. The tube is dated August 1993 & is manufactured by Aerotech.
Inside the box is the usual 2.2Ah 12v Li-Po battery pack & the brick type He-Ne laser supply. The small circuit in the centre is a switchmode converter that drops the 12v from the battery pack to the 5v required for the laser supply.
Here’s a couple of beamshots from the new laser, running at full power.
Here is a followup from the 1.5W laser module post.
The module has been fitted into a housing, with a 2.2Ah Li-Poly battery pack. Charging is accomplished with an external 12.6v DC power supply.
Above can be seen the pair of switches on the top, the keyswitch must be enabled for the laser to fire.
When armed, the ring around the push button illuminates blue, as a warning that the unit is armed.
Inside the unit. The Li-Poly battery pack is at the bottom, with it’s protection & charging circuitry on the top. The switches are wired in series, with the LED connected to illuminate when the keyswitch is turned to the ON position.
The push button applies power to the laser driver module, which regulates the input power to safely drive the semiconductor laser in the aluminium heatsink housing.
Here are a few details of a valve amplifier I am building, using the valve related parts from a 1960’s reel to reel tape recorder.
This amplifier is based on an a Mullard ECL82 triode/pentode valve, with an EM84 magic eye tube for level indication.
Here the first components are being soldered to the tags on the valve holder, there are so few components that a PCB is not required, everything can be rats-nested onto the valve holders.
Progressing with the amplifier section componentry, all resistors are either 1/2W or 2W.
Here the valve holders have been fitted, along with the output transformer, DC smoothing capacitor & the filament wiring, into the top of the plastic housing. At this point all the components that complete the amplifier section are soldered to the bottom of the right hand valve holder.
Starting the wiring between the valves & the power supply components. The volume control pot is fitted between the valve holders.
The valves here are test fitted into their sockets, the aluminium can at the back is a triple 32uF 250v electrolytic capacitor for smoothing the B+ rail.
First test of the amplifier, with the speaker from the 1960’s tape recorder from which the valves came from. the 200v DC B+ supply & the 6.3v AC filament supply is derived from the mains transformer in the background.
Here the magic eye tube has been fitted & is getting it’s initial tuning to the amplifier section. This requires selecting combinations of anode & grid resistors to set the gap between the bars while at no signal & picking a coupling RC network to give the desired response curve.
Here both valves are fitted & the unit is sitting on it’s case for final audio testing. the cathodes of the ECL82 can be clearly seen glowing dull red here.
In the final section, I will build a SMPS power supply into the unit to allow it to be powered from a single 12v DC power supply.
