SmaTrig 2.1

EOS battery grip disassembled

No-name EOS 400D grip disassembled
Canon BG-E2 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
1Ribbon connector: to AV, AE and AF button
2Ribbon connector: camera
3Battery connector
4Ribbon connector: to dial wheel and shutter button
5Grip on/off
64953 - Dual P-Channel MOSFET
7GE4435 - P-Channel MOSFET
8LMV393 - Dual low voltage comp (TI)
9Battery door switch
#PCB bottom side
1Battery tray switch
2MC14066BCP - Quad Analog Switch/Quad Multiplexer (ON)
3F200L - 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.

Dial wheel

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)

BG-E2 battry grip disassembly

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.

Comments (11)

Best Heart Rate Monitor
Really informative site
#11 - Best Heart Rate Monitor - 12/24/2011 - 16:44
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,
#10 - Ninoslav Adzibaba - 10/20/2009 - 15:46
Hi Tim,

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.

Best regards

#9 - Norbert Löv - 10/10/2009 - 16:10
Connector inside battery compartment of EOS 500D
Hi Luke,

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.
#8 - Tim Pope - 10/07/2009 - 20:52
HDR Grip is a great solution :)
Hi Luke,

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:

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,
Ninoslav Adzibaba
#7 - Ninoslav Adzibaba - 09/25/2009 - 08:00
ATtiny25 is build into my grip now
Hi Luke,

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!

Best regards


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.

#6 - Norbert Löv - 09/10/2009 - 18:27
Another example movie
Cause of missing the knowlegde of writing smaller code I bought a ATtiny85 yesterday to fill it with my large modification of HDR Jack...

I put a movie online which shows a sequence between 1/1000 and 15 seconds...

#5 - Norbert Löv - 09/04/2009 - 08:17
Movie of bracketing timer in action
First test work fine...

In the moment I use the interval timer, focus impulse adjust expose time, shutter impulse take the picture.

See here
#4 - Norbert Löv - 08/27/2009 - 13:41
Successful connected to BG-E2
Hi Luke,

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!

#3 - Norbert Löv - 08/25/2009 - 15:56
Sounds Great!

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.
#2 - Bjoern - 08/18/2009 - 11:19
Great idea!!!
Hi Luk,

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!

Best regards

#1 - Norbert Löv - 08/17/2009 - 20:10
E-mail (Will not appear online)
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