It can be done! This requires a new 2032 size battery, a sharp knife, small screwdriver and a bit of patience. See the photos for more details.
Latest Entries »
One of my other hobbies is photography, and whilst I don’t spend as much time with the camera as I would like I still like to have plenty of power. I shoot with a 30D and/or 40D, which uses the old style BP-511/A Canon battery. The dilemna I had is that I would like to power my camera from a 12-14V source (such as a SLA battery) to get plenty of juice, but I need to provide the requisite 7.4V expected from the battery. There are two aspects to this – electronic compatibility and mechanical compatibility. Luckily the electronic compatability is easy (at least on the older models – I can’t speak for the new ones) as you just need to provide the expected 7.4V. Mechanically I looked at a few options such as custom fabrications, but in the end I just settled for the tried and true “crack open a battery that no longer works”.
BP-511A Casing after removing cells and control board.
Daniel McCauley of http://www.easternvoltageresearch.com/ used to have a wonderful document that listed the current draw of a 300D when operating in different conditions. Whilst the document has long gone online, I recall that the peak current was in the range of about 1A, albeit for very short periods. It does however provide a rough estimate of the currents involved. I credit him with the original idea behind doing this as well!
Whilst the original design Daniel provided used a standard linear regulator, I figured that the size of switch mode supplies had decreased enough such that it should be possible to mount an entire DC/DC converter inside the battery compartment. This way I can feed in any (reasonable) voltage and the camera will operate happily. Being a touch lazy (and enjoying other things then power supply design) I just grabbed a module off the shelf that was small, and had what I thought would be acceptable specifications (lowish ripple, high efficiency). I settled on the TI PTN78000W module (in the surface mount variety). It was then just a matter of designing a rudimentary board around it that contained a protection diode as well as some input and output filtering. If you would like a copy of the schematic feel free to contact me!
Testing the new DC/DC converter board for fit - and it does!
I opted to get this board professionally made as I wanted a nice reliable final product that worked in some pretty horrid conditions (cold, dampy, hot, dusty – all the usual suspects!). It was then time to get the hot plate out and do some soldering:
The board is assembled except for 3x 2.2uF 0805 caps (and the cable connectors!).
And that is where this first post ends – I need to order some caps that I apparently don’t have in my junk box. I’ll post again once it is assembled and tested.
Note: I did contemplate purchasing a non genuine one from eBay, but I liked the idea of having something that I knew was a bit more reliable. Ironically enough I trust my own fabrications more when connected to expensive equipment then the really cheap knockoffs.
One of the projects that I am tinkering with at the moment is the creation of an audio capture device that can be phase locked to an external reference. The primary reason for this is not chasing extremely high quality audio – the contrary in fact, I don’t particularly care for the audio quality. The crucial part in this application is the timeing of when the ADC samples – allowing an almost traceable time stamp to be placed on audio recordings. At the very least there will be minimal long term drift over a long recording, making relative time reconstruction possible.
To make this all possible I grabbed a TI PCM2900B USB Audio Codec and started designing a board around this. Normally this IC requires an external 12MHz crystal for operation, which is responsible for generating all the internal clock signals. I have chosen to instead couple the output from an IDT ISC525-01 Clock Generator to the clock input on the PCM2900B.
To make this as useful as possible I have designed assuming an external 10MHz 50 ohm input is used for the clock signal via an SMA connector. This seems to be the de-facto standard for most modern test equipment. The analog input is via a standard 4 pin 2.54mm header (left, right, 2 grounds), and the computer interface is USB.
Whilst none of this is all that ground breaking, I figured that I would share it with the world to help out anyone else that wishes to try this sort of thing.
Anyway, some photos of the prototype:
The prototype board fo the USB Sound Card - The chip on the LHS in the photo is the ICS525, and the chip on the right is the PCM2900B. No audio I/O is installed for testing.
The back of the prototype USB sound card - a couple vias and an SMA connector.
For testing I haven’t yet used any actual audio I/O. The main purpose was to test the ability to use an external clock with the IC – which worked well. I have now redesigned the board to be considerably smaller (though less versatile) to remove a number of jumpers I included “just incase the datasheet wasn’t quite correct”.
As far as the reference clock goes – I have succesfully used a 0-5V Square Wave output from a function generator, as well as the 1Vpp reference output on the rear of the function generator. Both worked as well as each other (which makes sense, as the input is AC coupled anyway!).
Schematics will come in a post soon, as will possibly a PCB layout for those that want to DIY. The entire project cost is pretty cheap (~$20 for components) and I have intentionally designed the board to be very simple to make.