ArnoLed

My latest DIY photo equipment : ArnoLed.

Arnoled is (very) simple LED illumination add-on unit for my ArnoSync setup.
The main goal is taking photos of moving objects, such as birds,  ect. at a high shutter speed with a natural background. ArnoLed can be seen as a small Flashlight with its own power-supply which produces a continue light beam only during the shutter operation cycle. 1/ 160 sec is the max. flash sync speed of a Sony A6000. Because a rolling shutter uses two curtains, the total shutter cycle takes several msec even at a shutter speed of 1/4000 sec ! The object must only be illuminated during this short time, so a lot of battery power can be  saved. Because there is no proper external sync signal available on the hotshoe of a Sony A6000 camera to initiate the illumination cycle at this shutter speeds, my ArnoSync controls this via an extra output port.

Dilemma :

When using a shutterspeed of 1/160 sec or lower with an external flash set at low power to freeze the movement, then the background looks mostly black !  When the picture is taken with a high shutter speed - such as 1/4000 sec - an external Flash can only be used in HSS ( High Speed Sync ) mode. HSS mode on a Sony A6000 can only be used with EFC ( Electronic First Curtain ) set to OFF.
With HSS mode in this mode the camera shutter lag would be more as 90 msec,  which is too high for my application. With EFC set to ON, the total camera shutter lag is about 20 msec - which is very good !

ArnoLed actually consist in 2 versions :

A DUMB Version : 

This version produces a light beam during the time that its input signal is driven low with an open-collector transistor or equivalent circuit. The power-supply of the DUMB version is a classic primary alkaline or rechargeable NiMH 9 Volt battery.Because the internal resistance of this type of batteries is mostly higher as 2 Ohm no driver is used at the moment.The LED is driven only during ca. 10 ms  at max. 3 Ampere when taking a picture ! Actually no power ON / OFF switch is foreseen because the unit draws very current (some micro amperes) in its standby mode.

A SMART Version 

This version is build around my favorite PIC12F675 micro-controller. The duration of the light beam is made variable by software or via hardware if a potmeter is added at the analog input of the PIC device. This ArnoLed version can be triggered via a status change on its input from an open-collector device. The power-supply of this SMART version uses 4 X 1.2 AAA NiMh batteries ( 5 V ). Also the internal resistance of the battery and wiring is used here as current limiter (no special LED driver).
Because the PIC device operates most of its time in sleep mode, also no power ON / OFF is strictly needed. This version can be very easy optically be triggered by any other master if a suitable photodetector circuit is connected to its input port. 

Construction :

The LED used in my ArnoLed module is a CREE XM-L6 chip mounted on a 20 mm star.

Ref : http://www.cree.com/led-components/media/documents/XLampXML.pdf

The maximum continuous current of this device is 3 Ampere. Light output is ca. 1000 lumens with a compact 5 mm X 5 mm footprint. The max. ON time of the LED is only 10 msec / picture, so a long battery life is guaranteed A typical fully charged 9 Volt battery can produce more as 1000 Flashes ! I'm still looking to experiment with even stronger or multiple LED's on 1 chip if they are affordable. The actual output device is a IRLZ34 N-Mosfet with logic gate compatability.

The light beam is focussed with a low-cost Bullseye Glass Lens with a diameter of 30 mm.

Ref : DX.com - Bullseye Glass Lens of 30 mm - SKU 43045

The lens can be focused easily to get an illuminated frame of about 25 by 25 cm (0.8 square feet ) at a distance of about 60 cm ( 2 feet ). Until now no special LED drivers are used in this prototypes. The output will be certainly be lower if the battery reaches its end of life, but for my current experiments this is not  a real problem.

So a DUMB version of the ArnoLed only consist of the following parts : 

- a Power Led CREE XM-L6 mounted on a 20 mm star.
- a Bulls-eye Lens of 30 mm mounted in an adapted (25 mm long) analog film canister
- a 5 cm long 25 mm diameter Cold Water Pipe to hold the lens with the Led.
- a 9 volt Alcaline primary or NiMh rechargable battery as power source
- an IRLZ34 Power Fet with logical compatible gate as output device.
- a Plastic Soap Box model as housing
- a Neodynium magnet on the bottom of the housing to fix it on the ArnoSync.

Results :

With a manual focussed Meike 50 mm E-mount lens mounted on my A6000 camera the diafragm is mostly set at F8. The shutter speed is set at its max : 1/4000 sec. The ISO value is set at 1250 or above. With this settings some more extra light to the object is needed during overcasted day's to eliminate noise ! My current setup uses two ArnoLed's - one master on the left, the other on the right as slave. They are  mounted on my ArnoSync rail. On a normal or sunny day the ArnoLed works also as a fill flash, so I hope it can eliminate some unwanted schadows.

Some Pictures taken with ArnoSync + ArnoLed

Pictures of the DUMB version ( prototype )

Pictures of the SMART version (prototype)

Two Arnoled's DUMB versions mounted on my ArnoSync 

To be continued ....

Frans Eggermont - Joannes Huyslaan 45 - B-8790 Waregem - Belgium - Europe

My email address : frans.eggermont@gmail.com
My Flickr account : https://www.flickr.com/photos/arnoldus1942/
My Twitter account : https://twitter.com/frans_eggermont