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.


Dial Wheel
The picture showing the dial wheel of the no-name grip is a bit confusing. It looks like the three contacts on the left are all connected. But this would render the whole wheel non-working since the third (middle) contact is constantly connected to the center ring. Could you clarify?
#16 - Frank Petersen - 11/28/2012 - 15:02
Apologies for adding to a very old post, but I'm hoping somebody sees my cry for help!

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!
#15 - Paul - 08/15/2012 - 12:03
Best Heart Rate Monitor
Really informative site
#14 - Best Heart Rate Monitor - 12/24/2011 - 17:44
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,
#13 - Ninoslav Adzibaba - 10/20/2009 - 17:46
HDR-Battery Grip
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.
#12 - luk - 10/16/2009 - 16:41
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

#11 - Norbert Löv - 10/10/2009 - 18:10
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.
#10 - Tim Pope - 10/07/2009 - 22:52
pinout of the battery grip?
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
#9 - Simon Claessen - 10/06/2009 - 23:40
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
#8 - Ninoslav Adzibaba - 09/25/2009 - 10:00
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.

#7 - Norbert Löv - 09/10/2009 - 20:27
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...

#6 - Norbert Löv - 09/04/2009 - 10:17
Modified HDR Jack Software controll my EOS 20D
Unfortunately the ATtiny25 only have 2k of memory and the modified software need more space...
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)
#5 - Norbert Löv - 09/03/2009 - 08:46
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 - 15:41
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 - 17:56
AVR into battery grip
Hi Luke,

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?

Best regards

#2 - Norbert Löv - 08/19/2009 - 20:35
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.
#1 - Bjoern - 08/18/2009 - 13:19
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

#0 - Norbert Löv - 08/17/2009 - 22:10
E-mail (Will not appear online)
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