Workbench Spot Light

Oct 21
Posted by justDIY Filed in LEDs, Project, Prototyping

The camera I added recently gained a new boom mounted partner, a Luxeon Rebel powered spot-light. Consisting of three 200+ lumen neutral-white Rebels, the spotlight puts a lot of light onto a spot on the workbench. I’m going to pick up a diffuser optic for the collimator so it’s not quite such a tight spot. I used a paint striping gun to reflow these little guys; surprisingly my solder paste from 2007 still works!

Before reflowing

Driving the Rebels is a 1a Buck Puck from LEDdymanics. It regulates a surplus unreglated 12v wall wart down to a safe current for the LEDs. I’ve added a potentiometer to the driver’s dimming input, giving me a little control over the amount of blinding from the light. The little circuit board uses a 5 position Molex connector to provide power to the LEDs and a cooling fan. I recycled a smallish northbridge heatsink fan to keep the leds happy.

I’ve rigged up a temporary mounting solution using a T and two more elbows.

Workbench Camera

Oct 21
Posted by justDIY Filed in General, Project

Seeing a few other Makers add simple camera & boom systems to their workbenches, I was inspired to do the same. I tried to keep the construction as simple as possible.

Camera Boom Track

My boom track consists of two 3/4 inch floor flanges, two 3/4 inch 90° elbows, NPT on one end, slip fitting on the other and a five foot length of 3/4 inch schedule 40 pvc. The boom arm consists of a 1″ x 1″ x 1/2″ T fitting, cut in half, several random lengths of 1/2″ schedule 40 pipe, two 90° elbows and a end cap drilled and fitted with a 1/4-20 bolt, nut and wing-nut.

Camera Mount

Nothing is glued, so far friction holds it all together. I figure I can add set-screws if the elbows start to slip too much.

The camera is a Microsoft Lifecam Studio, which is a 1080p sensor with a fixed aperture auto focus lens. It’s a cell phone camera basically, when you get it to focus, it does a decent job. I’ve only recorded in 720p, I haven’t found the option to record video in 1080p, maybe my PC isn’t fast enough.

Pentax IR Interval Timer

May 30
Posted by justDIY Filed in Control, LEDs, Microcontroller, Project

Hey, look at that, my blog website is still alive and working. Last post was Sep 2010, a long time ago.

I’m planning a trip to the desert, and one of the things I wanted to make for myself were time lapse movies of sunrise or sunset, and the night sky. My DSLR does not have a wired remote capability and Hoya has decided not to include an interval timer on their low end DSLR

I could have purchased a timer off ebay, that claims to be compatible with every DSLR ever made but those claims make me skeptical. I also did not care for their user interface. So, many months ago, I tore apart one of the Pentax IR remotes, to see what makes it tick. It was a simple design on the inside, a rather large micro-controller with external clock, a transistor, a capacitor, a few resistors and an LED. The trigger button was one of those resistive pad-switch types. Originally I thought I could just trigger the remote by pulling one side or the other end of the button high or low. This did not work, and when I scoped it, I discovered a handshake was employed between the two terminals of the switch, both leading to micro-controller pins. So it looks like Hoya didn’t want people hacking the remote directly.

Switching to plan B, I tore apart an old pioneer cd changer and harvested its IR decoder chip. Following some arduino code from Lady Ada, I tried to capture the timings of the IR signal using a PIC. This worked to a degree, and probably warrants further study down the road, but I couldn’t get the pulse train quite right and so the camera would not respond.

Abandoning the learning-remote line of thought, I connected the IR decoder to my o-scope and manually measured the pulse train. It was only 26 msec, and consisted of 15 transitions. 13 msec on, 2.8 msec off, and then 1 msec on/off repeated eight more times. Using the 12F683 chip (one of my favorites), I had access to an 8MHZ internal clock and a hardware PWM module. Microchip claims the hardware pwm maxes out at 20khz, but I had no trouble getting a stable 37khz carrier out of it. Then I whipped up a little subroutine in proton basic which toggled the carrier on and off with the appropriate timings. I had setup the pic’s pwm output on channel 1 of the scope, and output of the ir decoder on channel 2. I could fire the pentax remote at the decoder and compare it to my pulse train from the pic. When they were an exact match, I got the camera and presto, it started snapping pictures.

Cam Remote Schematic

That schematic is what I’ve worked out for a bare-bones version of the remote. A single button is used to program the interval, there’s a status led and room for two IR emitters. My current prototype is only using one emitter, because that is all I have right now. I’m also using a 2N3904 which isn’t ideal, but it was working on the breadboard and now it’s soldered in place. I just now looked up the specs, and the poor thing is only rated at 200ma collector current – that could explain the lack of output power I’m seeing on the emitter.

In interest of saving time, I didn’t make a PCB for this revision, but I’ll probably do that for the next prototype. All point to point wiring, I tried to be neat. I used a tiny SMT resistor to drive the transistor, it worked out real handy.

The timer and two AA batteries fit in this mint tin I’ve been saving for years. I don’t know if they are still in production; I would like to get a few more.

I field tested the timer at tonight’s sunset – I’m trying to figure out how to convert a bunch of jpeg’s into an avi now – stay tuned!

Update: Here’s the video, turns out Picasa can generate a timelapse … only 8 seconds, need more frames!

Mint Tin Bike Light Continues

Sep 18
Posted by justDIY Filed in LEDs, Microcontroller, Power, Project, Prototyping

As the (normal) bicycling season draws to a close for my latitude, I’m nearing completion on my bicycle taillight project. I sent out a few weeks ago for some professionally fabricated pcbs and as usual, they look great. There were a few bugs that were entirely my fault, but nothing serious enough to stop the pcb from doing its job.

bicycle taillight pcb assembled

I added two “features” to the pcb before sending the design out, both of which were untested in the initial prototypes. The main feature I wanted to have was “motion detection”, so the taillight would shut down should the bike become idle for a period of time. No need to be wasting precious photons while the bike is leaned up against a tree or parked in a bike rack. Motion detection is provided by a roller ball switch, intended to replace the old fashioned mercury switch. A tiny gold plated ball rolls around in a plastic and metal cage, completing electrical circuits during its travel. The light’s micro-controller recognizes these impulses and continues to let the light function. As soon as the tilt switch stops changing state, resting as either a short or open circuit, the uC begins a count. When that count totals some arbitrary number, the light returns to a standby mode with the SMPS in shutdown. The uC then watches the tilt sensor for the state to change again and upon a change, resumes the previous operational mode.

The second feature is a battery minder circuit. Using a 2.5v precision reference, the micro-controller samples the battery voltage using its on board ADC. The idea is to detect a weak battery condition and operate the SMPS at a lower duty cycle, to make the most of the remaining power. The assumption here is that some light is better than no light in terms of safety. One of my pcb bugs lies in this circuit. The Microchip 12F683 uC I selected for this project is an 8 pin device. Its voltage reference pin is also multiplexed with the programming clock. In my design, I had made the error of connecting the vref pin directly to the voltage reference output, which is biased with a 1k resistor to the Vdd rail (bat +). So effectively, I have a very strong pull-up to 2.5v on that pin. This made programming the PIC impossible as it could not detect clock transitions. I will try salvaging these PCBs by changing to a 10k or 20k bias resistor on the reference, or cutting the trace leading to the Vref pin and soldering a 10k+ resistor in series, since we don’t need any current on that pin, just voltage.

Once I polish the code a bit more, I’ll be looking for a few folks to send a sample units to in exchange for reviews and feedback, down the road I would like to sell these either as a kit or a pre-assembled unit.

Fresh PCBs

Sep 16
Posted by justDIY Filed in LEDs, Picture, Power, Project, Prototyping

I just received these FedEX on Tuesday, fresh from China via Colorado.

taillight stack small

headlight stack small

The first stack of boards is the prototype taillight driver, sporting a tilt switch for motion detection. The second board is a pretty similar design, with a bigger inductor and more compact layout. The intention here is to run a trio of Lumiled’s Rebel leds at 0.5 to 1w each off 4AA batteries, for a compact self contained headlight. More details on that idea later!