EOS battery grip disassembled
In the following the inner workings of two Canon EOS battery grips will be shown. The motivation to disassemble the grip came from the idea to gain control of the camera buttons and wheels without opening the camera body. By connecting a microcontroller to the dial wheel and the shutter button in the battery grip, functions not included in (or intentionally excluded from) the camera firmware, such as unlimited exposure bracketing, can be implemented.
No-name EOS 350D/400D battery grip
To release the dial wheel and shutter cover, two screws inside the grip must be loosen.
The on/off switch disables the buttons and the wheel on the grip. It has no influence on the power supply.
The four screws in the bottom plate are covered by a rubber sheet. The
rubber can be pulled off easily. It is possible to re-attach it after reassembly
without any difficulty. The glue stays very adhesive (and stinks terribly).
The covered screws can also be located by looking through the battery chamber door.
The following images show the PCB inside the grip. Fortunately there are no purely digital components on the PCB, meaning that the communication between the grip and the camera body is not based on digital codes as in the EF lens interface or the flash connector. Most of the electronics seem to deal with the control of the batteries (comparator, MOSFETs).
I could identify all the important parts on the PCB and listed them in the table below.
|#||PCB top side|
|1||Ribbon connector: to AV, AE and AF button|
|2||Ribbon connector: camera|
|4||Ribbon connector: to dial wheel and shutter button|
|6||4953 - Dual P-Channel MOSFET|
|7||GE4435 - P-Channel MOSFET|
|8||LMV393 - Dual low voltage comp (TI)|
|9||Battery door switch|
|#||PCB bottom side|
|1||Battery tray switch|
|2||MC14066BCP - Quad Analog Switch/Quad Multiplexer (ON)|
|3||F200L - PTC Resettable Fuse|
To remove the ribbon cables from the connectors, the latch must be released, compare 1 (closed) and 4 (open) in the top side image of the PCB.
Ok, let's have a look on the most interesting part - the dial wheel.
The functional principle is rather simple.
There are three contacts sliding over a contact disk with a star-shaped
conducting surface. One is in permanent connection, the others are
connected with the star when the disk is rotating. Because the "arms"
of the star are located at a different angle for both contacts, the rotation
direction can be detected. For clockwise rotation (see image) the right
contact will connect first, for counter-clockwise rotation the left one
will be first.
The dial wheel doesn't give that nice click like the original one in the camera body. It's a little bit to soft, but faster then the original.
Canon BG-E2 battry grip (20D)
The following pictures were made by Norbert Löv during the modification of his original Canon BG-E2 battery grip for external bracketing control. Click on the thumbnails to view the image.
I have the BG-E4 grip for my 5D, and the - button (AE lock/zoom out) on the grip has stopped working. I use that button for auto focus and so I'm a bit stuck without it.
Any ideas what the problem may be?
Thanks for any help anyone can offer!
next version of our hw platform is actually omitting transistors and we are using pin circuit and ddr register switching instead. I will let you know when we publish something...
All the best,
Many thanks for the info on your project. Please let me know if you publish more on the project. What was the driving idea for the circuit?
BTW: you can omit transistors pulling the wires down. You can do it just by chnanging a port pin of the AVR form input to output with logical zero.
Please contact Norbert Löv for the battery grip connector pinout.
please send me a mail or give me a email address if you wish to have the pinout of the 16 pin port inside the battery compartment in a 20D battery.
I wonder whether you can help me, I am looking to interface a mobile
phone to my EOS 500D/Rebel T1i (using an AVR to convert serial from
phone to whatever needed by EOS).
What interests me is the 16 pin port inside the battery compartment as
this seems like it may be my interface... however I cannot find any
real pinout or information on this connector.
reading your posting about the innards of the battery grip i had one big question: what is the pinout of the control signals to the camera body. i assume that the switches are connected without electronics (except for the main switching array to the pins on top. but whitch pin is connected to whitch switch?
i want to build a HDR battery adapter not sticking out of the camera with a external powerpack but internal microcontroller. a dead battery will be the casing for this
just to say that implanting microcontroller in the battery grip is a way to go! I had the same idea and manage to complete it a few months ago with the help of my friend Aleksandar Zivkovic. Since then I'm using with no problems.
We used ATtiny2313 with BG-E2 grip, and here is our schematic: http://www.kultdizajn.rs/tmp/schematic.jpg
We have been planning to also publish our work in a few weeks with new, improved version. If you need anything form us - we'll be glad to help!
All the best,
based on your HDR Jack1 Software and with the fuctions you send me included I have a HDR timer now which works great!
Thanks for your support, I look forward for a HDR Jack version which is optimized for the grip... ;-)
Here another sample movie with a very fast expose time adjustment!
P.S.: I drilled a whole on the left side of the grip and placed a switch there (look like the same switch you use in the HDR Jack2.
I put a movie online which shows a sequence between 1/1000 and 15 seconds...
Therefor I will buy a ATtiny85 today.
Here a sequence who started with expose time of 1/4000, take a shot and increase the expose time by 1ev(3 steps of the dial wheel) after each shot(just one more test)...
See here(bad quality, but enough to see that it work)
In the moment I use the interval timer, focus impulse adjust expose time, shutter impulse take the picture.
for the first tests I connect some wires to the focus, shutter and dial wheel contacts.
I have control to the functions we need to adjust the camera by remote.
Now a piece of software would be fine... ;-)
Here a link to the pictures which shows the disassembling, the soldering inside and the way my temporary cable comes out of the grip.
When there is software and everything works fine, I will look for a nice connector which will be build into the case of the grip!
thanks for your great page, It's amazing how much useful information
you put together here!
You did such a great job!
Since I used your HDR Jack2 and read this article about the battery grip I cannot stop to think about a bracketing timer connected to my battery grip...
I don't plan to build the AVR into the grip, even there is enough space.
I would prefer a 5 pin connector which is build in the grip.
The connector would be connected to focus, shutter, dial wheel contact1, dial wheel contact2 and ground), may a Lemo connector would be fine.
With a connector you would be free in the choice what to connect.
This could be a modified HDR Jack2,
or a AVR Butterfly board if a display is wanted,
or even a cheap box with 4 switches as a wired soulution.
Anyway, I'm sure a lot of people out there will be interested in something like this.
I defently take my battery grip apart soon and connect wires to the switches inside!
Is the middle contact of the dial wheel on ground level and short contact1 or contact2 to ground, or is it used as a 2 way switch?
as owner of a 500D (which is listed with 1/8s as shortest EXP Time with HDRJack2) i'm very interested in this Project.
Hopefully you'll find a way to get this up and running.
I'm very interested in this project and it would be nice to share information.
I think to connect to the switches in the grip will be a perfect solution to do exposure bracketing.
It will produce correct exif information and give the posibility to do expose times less that 1/60 (which is the limit via HDR Jack on my 20D) in daytime.
Please let us get in contact to discuss the details and to find out howmuch we can share!