Controller for Melles Griot electronic shutters

Melles Griot Nr. 3 Electronic shutter with thread adapter rings.

Abstract: A microprocessor controlled shutter control-box for electrically driven shutters such as the MELLES GRIOT 04 IES 003 and others, such as the ILEX electric shutters. A SGS-Thomson ST6215 is used as the microcontroller.

Older view camera lenses often come in shutters that have problems from use or age. Usually a clean/lube/adjust service will restore the shutter but sometimes it is necessary to replace it. New Copal shutters are very expensive and used shutters in good working condition are rare and also not cheap, especially the large (Nr.3) sizes. Not to speak of the electronic Copal and Sinar shutters.
An inexpensive alternnative are the Melles Griot electric shutters that appear on ebay now and then and usually go for well under 100$, mainly because the necessary controller box costs 800$ and has limited capabilities.
This page describes the construction of an inexpensive controller with very high accuracy, many features and comfortable handling. An inexpensive ST 6215 microprocessor is used (mainly because I have the SGS starter kit). PIC- Atmel- or other microcontrollers would do the job as well if programmed accordingly.

Features:

short times:1/125 1/60, 1/30, 1/16, 1/8, 1/4, 1/2, 1/1 sec. (shortest time limited by shutter)
long times: 1sec. to 255 sec. in one second steps.
B Bulb mode: shutter is open while button is pressed
T Toggle mode: button toggles shutter open/close
Self timer: 10, 20, 30 seconds self timer with short time modes.
flash sync: flash sync right before closing shutter.
LED
- flashes 3x on power on
- flashes 6x fast when triggered with an invalid speed setting
- lights during self timer countdown
overvoltage opening pulse for fast opening, low holding voltage for fast closing.

Operation

the controller has four coding switches the first going from 0 to F and the other three going from 0 to 9

long time mode: when the first switch is set to 0 all four switches are interpreted as time n seconds
examples: 0005 is 5 s and 0120 is 120 s= 2 min
maximum is 255 s =4 min 15 s

short time mode: when the first switch is set to A the remaining three switches are interpreted as fractions of a second.
The following times are possible: 1/64, 1/32, 1/16, 1/8, 1/4, 1/2, 1 sec. all other settings result in an error message (LED flashes 6x) when the shutter is triggered.
examples: A064 is 1/64th, A008 is 1/8th, A025 or A732 will result in an error.

"B" (Bulb) mode: When the first switch is set to B the shutter acts like any camera in "B"-mode: the shutter is open as long as the trigger is pressed.

"T" (Toggle mode): When the first switch is set to C pressing the shutter button will open the shutter, pressing it again will close it.

Self timer modes When the first switch is set to D,E or F the self timer is active.
the remaining three digits are interpreted like in short time mode. D gives a delay of 10 s, E of 20s and F of 30 s
example: E064 will open the shutser for 1/64th after 20s delay.

Circuit diagram(This is not the final one yet!)

Click here for the final circuit (625 MB !)

Hardware

Shutter voltages

Melles Griot shutters come with different voltage ratings, most common is 48V.
To archieve optimal shutter performance, MG recommends to open the shutter at 4x the rated voltage and then hold it open at half the rated voltage to minimize heating the solenoid and to speed up closing.
Therefore there is a double power supply for the shutter:
A capacitor is charged up to U(open) =4x U(shutter) through R(charge) in about one second. After the Capacitor has discharged into the shutter R(charge) keeps the current from the high voltage supply low while the lower Supply U(hold) keeps the shutter open until the Transistor closes.

Transistor

The shutter driver can be any power FET or darlington that sustains the voltage which is used (Add some reserve).
I use a BUK102 power fet.

Flash sync output

The flash sync output is the same as in my Polaroid SX-70 flash adapters. It works with most electronic flashes however some flashes have a low voltage DC trigger circuit which is better served with a transistor type optocoupler.

Software

Program listings. Version 8 works perfectly.
Flash sync now works in all modes.
Repetition rate changed from 1 sec. to 1/2 sec.
1 sec setting added to short time mode (can now be 0001 or A001)

Photos of the controller and the shutter

Prototype Hardware. The Hardware is so simple that it can easily be built on a Vero Board(R).

Hardware

A power-on reset was added for safe starting (1 microfarad+10 KOhms).

The outputs of port C can only source 5 mA. I should have used 4 lines of port C which can source 20 mA which is sufficient for LEDs.
Therefore I had to add three open collector drivers (BC547B)

The processor is very sensitive to power supply spikes.
I use a shutter with a 6V solenoid and first intended to share the holding voltage with the processor's power supply. This was not a good idea. I now have two completely separated power supplies for uC and shutter. with one 5V-supply for the processor and a 8V+22V-supply for the shutter.

I decided to use coding switches in the controller because they can serve as input devices, displays and even memories at the same time.
However a rotary input dial with an separate display might be more comfortable as a user interface

Things that could be added

At the moment the modes 0XXX to 9XXX are not used
they could be used for an expanded longtime range of up to 9999 seconds, or for other features, such as an interval timer (but who needs that on a view camera)

The short time ranges, are now 1/1 1/2 1/4 1/8 1/16 1/30 1/60 1/120 with no intermediate values allowed. Maybe it is better to allow any short time setting. Who wants to write the math routine?

Anyone wants to make a pcb-layout to be be published here ? I'd trade a programmed processor for a PCB.(I am quite happy with the Veroboard prototype though)
Preferably one including a power supply for 6V and 48V shutters.

Do you have any suggestions ? please email me.

I don't sell these shutter controllers

I you are interested in building your own controller feel free to ask me if you have any problems or if you are looking for a programmed microcontroller.