Benchtop power supplies

I have designed and build several power supplies over the years, below is a photo of two of them:

Electronic workbench

This is a project I am currently working on. It contains a 12Vdc drill speed controller, 3 power supplies, an audio amplifier as well as a signal generator. Below is a photo of the unit:

I have recently made a new front panel legend using Tango. Below is a photo of the new front panel:

Audio digital signal processor

This is an experimental setup which I have decided to build into a box. I used a Texas Instruments TMS320C31 starter kit board for the signal processor. I made a board on which the audio codec board as well as the DSP board plugs into. This base board also contained the memory, which is needed for delay and reverb effects. The audio codec I used is a Crystal CS4222 20-bit stereo audio codec. Below is a photo of the signal processor:

The unit in the center is part of a Texas Instruments TMS320C31 starter kit. The IC's to the right on the main board are static RAM IC's. The board to the left with the RCA connectors mounted on it contains the CS4222 audio codec. The board on top of this board is used to interface the CS4222 to the TMS320C31 DSP.

The DSP starter kit board connects to the PC via the printer port. I wrote software for the PC with which effect parameters can be altered and download to the DSP.

For a schematic of my interface board click  here .

DC Motor Servo Controller PC Card

I have designed this card to be used in a milling machine. This card is capable of controlling 4 DC motors. This is an experimental card which I have not finished, since I no longer had a need for it. Below is a photo of the card:

The left side of the card contains 4 12-bit digital to analog convertors and signal buffering circuitry which is used to control the drives. The 4 DB9 connectors on top of the board connects to the optical shaft encoders of each axis. Just below the DB9 connectors are the SN75175 line receivers which conditions the signals from the optical shaft encoders. Below these the four empty slots for the PIC microcontrollers may be seen. I intended to use PIC16F84 microcontrollers as counters to count the pulses from the optical shaft encoders. The DB9 connector on the back plate of the card is used for connecting home or limit switches. The opto-isolators which is used to isolate the sensitive electronics from the home or limit switches is just to the left of the DB9 connector. The four RCA connectors connects to the DC servo drives. The remainder of the components includes a crystal oscillator for the PIC's as well as address decoding logic. The DIP switches are used to set the card's base address. Although this is a 8-bit interface ISA card, I have added the 16-bit extension to the bottom of the card for additional mechanical stability.

Analog Interface PC card

I have had a few 12-bit DACs as well as a 16 channel 8-bit ADC in my spares box, so I decided to build a ADC/DAC card. Below is a photo of the card:

This card has 3 12-bit digital to analog convertors as well as a 16 channel multiplexed 8-bit analog to digital convertor. It also has 3 4-bit DAC's which I have implemented using op-amps. I used 3 8255's for interfacing the DAC's and ADC.

Additional projects:

Computer A/D and D/A card:
This card was designed in the time when computer soundcards were still considered expensive. It contained an 8-bit DAC as well as an 8-bit ADC.

Microcontroller for portable incubator for babies:
This project consisted of a ST6 microcontroller which was interfaced to a membrane keypad and an intelligent LCD display. The microcontroller was used to control the temperature of the incubator. It also interfaced to analog electronics, not designed by me, which monitored the baby's vital signs. If the heartrate or breathing rate went outside limits, settable using the keypad, an alarm will sound.

Lift controller:
This project consisted of a 8031-microcontroller which was interfaced with switches and relays to control a lift. The lift had four stations.

Drill speed controller
This speed controller is used to control the speed of a 12VDC PCB drill. It consisted of a 12V power supply and a adjustable switchmode regulator.

Stepper motor drive and control software for flow rate generator:
This flow rate generator consisted of a syringe with a plunger which is connected to a stepper motor. The software on the PC is used to accelerate the plunger to a certain speed.

Home alarms:

I have build several home alarm systems over the years for my house. I build the first alarm system in 1988. It was a 4 channel design.
This was the first more formal alarm system which I have build. It was a very simple alarm system, it had four loops with bypass switches. If a loop was broken, the alarm sounded until the loop was restored and the alarm resetted.

In 1992 after we had a burglary I decided to build a better burglar alarm. The system had a total of 10 channels. All sensors were connected onto a single 4-core cable. This alarm had battery backup as well as a buzzer. It primarily made use of PIR sensors, although I have added magnetic switches to some of the doors just for a backup.

In 2000 I decided to upgrade the above system as the previous system used CMOS logic without any microcontrollers. The new system is based on a ST6 microcontroller. It only has 8 channels which is grouped into two 4-channel groups. Each 4-channel group works on its own multiplexed cable.

Camera protocol analyses of ARRIflex and Moviecam cameras:

I have done some contract work for a company who needed to know the communications protocols of both the ARRI and Moviecam cameras. In the case of the ARRI cameras I have analyzed the communications protocol between the camera and the RCU (remote control unit.) In the end I was able to eavesdrop on the communications and was able to display camera parameters on my PC screen. I was also able to control the camera from the PC without using a RCU. I also emulated a camera on the PC, to enable me to test a RCU without having a camera available.

In case of the Moviecam camera I only came to the point of displaying camera parameters on my PC screen. If I had a Moviecam camera longer available I would also have been able to control the camera from the PC.

Design of TV test pattern generator:

I am currently designing the electronics for a TV test pattern generator. I have already made a trail version using a PIC16F84 and a Analog devices AD724 to generate a colour bar test signal.

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