Project: CRT Oscilloscope LCD Mod – Simulating signals

After putting this project on the back burner, I am focusing on it once again. Brian HG on the EEVblog forums suggested that a simple line doubler would make the signal compatible with most modern VGA displays. What that means is that each line in the frame needs to be repeated twice, at double the speed.

Currently we get a new line every 40 microseconds, but this is too slow for most displays to be happy about. Therefore, if we record each line and output it twice at 20 microseconds each most VGA displays will be ok with it.

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Project: Robox – Buttons: Interrupts or Polling?

The robot box needs to know when it has reached the limit of it’s motion. If motion continues past this point, the machine will literally rip itself apart. To stop this happening, I am using a limit switch that will be pressed if the robotic finger move too far. However, it seemed that a good portion of the time the robot would ignore this button and continue to rip itself apart. The reason for this lies in the way I was using interrupts to detect the pressing of the button.

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Project: Nixie Clock – MC34063 Boost Converter (upgrade)

I really like my Nixie Clock that I built two years ago – but I don’t like to leave it on when I’m not around. The reason for this is that the Nixie tubes are powered directly from the mains which means that touching the Nixie tubes could result in a dangerous electric shock. While the tubes are protected under glass I don’t like the thought of someone accidentally tripping over it and getting electrocuted. So I decided to redesign the clock.

I am going to power the clock from a 9V wall supply and boost that voltage up to 180V to light the Nixie tubes. While this is still quite a high voltage, it is isolated from the mains and is much less dangerous.

My design is largely based on Threeneuron’s Pile o’Poo.

power_supply_schematic.png

The schematic for the 180V power supply

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Micro Motor Controller – Code and Gerbers

For the Robox project,  I needed a board to program and control a servo and a DC motor – I could probably have used something off-the-shelf, but I prefer to have a board specialised for the job.

The board I designed features an ATtiny828 microcontroller with 16 general use IO, two PWM outputs to control two 6V servos and an Allegro A3916 dual h-bridge to control two DC motors (or one stepper motor) at up to 1A per channel. This is more of a general use motor control board and could be useful in a bunch of projects.

Schematic-v1.0.png

Schematic

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Project: Robox – Modifying Servo

I needed a servo for the robotic finger so that it could go forwards and backwards in a controlled manner to push the switches. Servos normally have limited rotation e.g. 180 degrees but I accidentally ordered a continuous servo which means that the motor spins continuously and instead of controlling the angle of the motor, you control the speed of rotation. This is obviously not OK because I would not be able to move the finger reliably. However I realised that it was well suited to the motor driving the threaded rod.

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