“The Purge: Election Year” Mask

Constructed in half an hour using a plastic Halloween mask and a length of green electro-luminescent (EL) wire, this project was first suggested to me by my friend and peer over at Starboard Engineering. This project required a steady hand to precisely drill the holes and careful planning to ensure the most efficient route when threading the EL wire through the mask. We have a bunch of masks available but order now to avoid disappointment.

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Solid State Cabin Blower Resistor

A while ago the cabin fan in my car stopped working at lower speeds. Looking through the schematic diagram of the heater controls (courtesy of a Haynes manual) revealed that the motor speed was being crudely controlled by putting various large current limiting resistors in series with the motor. Upon inspection, the large wire wound resistor pack was cracked and a quick test with the multimeter confirmed my thoughts, there was no continuity across  the two larger resistors for speed settings 2 and 3 (out of 4). I confirmed that it was only the resistors causing the problems by putting a wire in parallel with the resistor effectively by-passing it and confirming that the Fan ran at max speed.

Original Resistor Pack

Original Resistor Pack

I decided it would be a good opportunity to design a PWM speed controller to be compatible with the car’s pre-existing system. Two options came to mind immediately, the first was using a 555 timer and the other was using an Atmel ATTiny 85, both of which I had in my parts bin.

The two options would require a potentiometer to be put in the place of the original 5 position rotary switch but the 555 timer would need a lot more care to ensure that it would go from 0%  to 100% duty cycle across the 80 degrees of motion that the original dial markings were spread across. Using a microcontroller would allow a map to be created and make full use of the limited potentiometer travel with ease. Not only would it make fine tuning easier, it would also allow the PWM frequency to be experimented with.

Here was a simple schematic I quickly threw together. The top left rectangle is the isp connector and the one on the right is a 4 pin solder pad. The large N-channel Mosfet is driven by VCC and is turned off by powering the NPN which in turn shunts the pull-up resistor.

The circuit consisted of a LM7805 voltage regulator and capacitor bank to supply a clean source of power the Atmel ATTiny 85. A large N-channel Mosfet was used to allow the current to flow from the motor to ground. It was driven by the VCC rail and is turned off by powering the NPN which in turn shunts the pull-up resistor to ground, intern bringing the gate of the MOSFET to ground. The circuit was designed in Eagle Cad and sent off to OSHPark PCB FAB.

 

The final 2 layer PCB

The final 2 layer PCB

I used the eagleUP  plugin for eagle and google SketchUp to create a 3d model of the board and the populated it with parts to ensure that the heatsink would fit.

SSCBRP

I used the eagleUP plugin for eagle and google SketchUp to create a 3d model of the board and the populated it with parts to ensure that the heatsink would fit.

 

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I didn’t have any smaller capacitors so unfortunately I had to make do.

 

The potentiometer was epoxied into the carcass of the old switch.

The potentiometer was epoxied into the carcass of the old switch.

 

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The final product with a heat-sink and potentiometer attached.

The final product with a heat-sink and potentiometer attached.

 

The design was successfully implemeted into my car however a small compromise had to be made. With the PWM frequency set above the human audible range (20KHz) the MOSFET was overheating. It is possible that the MOSFET was not fully saturated but it is more likely becauase high frequency switching causes the it to spend longer in the transistion region which wastes power. To overcome this, the PWM frequency was reduced  to 10KHz which does produce a faint whine under normal operation.

Arduslider

This arduino controlled, motorized camera slider uses both 3D printed parts and and 3D printer parts. It costs a fraction of the price of commercially available sliders and can be modified to suit you.

The video below was shot at Dartmoor National Park using this slider. The last 2 clips were done by combining this project with my earlier D40 remote hack to create a moving time lapse. Please view it in 1080p if you have the bandwidth…

 

Video

 

The dual rail design was inspired by a cliff elevator. The beauty of this design is that the two slider heads move in different directions and allow a camera to move further for a given length slider. It later came to light that a start-up on kickstarter had already implemented this design and had started the patent process. It looks like a really nice piece of kit, however it is far beyond what I was willing to spend with my limited filming experience.

 

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Arduslide: Arduino Camera slider

 

 

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Concept: counter slider mechanism

 

Required Parts:

  • 2x 1/4″ BSW x 1/2″ Long Whitworth Hex Bolt, Nut and Washer.
  • 2x M3 14mm bolts
  • 1x Nema 17 stepper motor
  • 1x Pololu A4988 Step Stick
  • 1x Arduino Nano, Uno or Leonardo.
  • 1x Veroboard / Stripboard
  • 1x DPDT Toggle Switch
  • 1x 10K Potentiometer
  • 1x Decorative Knob
  • 1x Smooth Idler Pulley Kit
  • 2x Sub-Minature Micro Switches
  • 1x GT2 Timing Belt: 2mm Pitch, 6mm Wide, 700mm Long
  • 4x Hardened Steel Smooth Rods: 8mm Outer Dia, 300mm Long
  • 1x Aluminum Round Tube, 1/2″ Outer Dia, 16swg Wall Thickness, 300mm Long
  • 12x LM8UU linear bearings, (8 are used but get 12 as they are damaged easily)

Optional Parts:

  • Camera Remote
  • DC Boost Regulator
  • USB Power Bank
  • USB Cable
  • 1/4″ Ball Head Tripod Camera Mount
Bits and bobs.

Bits and bobs.

 

Printed parts.

Printed parts.

 

Slider bearing fitment

Slider bearing fitment.

 

Rails and limit switches in place.

Rails and limit switches in place.

Portable Boombox

Earlier last year my University house mates and I had house party, in order to provide ample volume and substantial bass I decided to up upgrade from a pair of bookshelf speakers to an all in one, easy to carry sound solution. At the heart of the boombox is a 200W RMS car stereo amplifier, which is more than capable of driving the twin 75W mid/bass drivers.

The system has a 9AH sealed lead acid (SLA) battery, a mains powered battery charger and a high current 12V switch mode power supply in the form of a 203W xbox power supply. A large triple throw rocker switch allows the desired power source to be selected and the smaller rocker switch puts the xbox power supply in sleep mode or awakens in depending on the position.

When a powered IEC (kettle cable) is inserted, the battery management system immediately begins to charge and then maintain the level of the battery.

Powerful portable boombox

Powerful portable boombox

 

Boombox internals.

Boombox internals.

 

Video

 

Interface panel

Interface panel

 

Schematic Diagram

Schematic Diagram

 

How to build!

This project was documented on Instructables.com, click the button above to visit the page.