Some details of converting my Nikon inverted diaphot from AC to DC

Here you can discuss DIY adaptations to the microscope.
Post Reply
Message
Author
macnmotion
Posts: 523
Joined: Mon Sep 26, 2022 3:13 am

Some details of converting my Nikon inverted diaphot from AC to DC

#1 Post by macnmotion » Sun Nov 06, 2022 10:46 pm

I have converted my Nikon inverted diaphot from AC to DC to control the 50 watt halogen bulb. The original microscope's AC power runs through a dimmer that changes voltage to control lamp brightness. I quickly discovered that the 50hz AC power here in Thailand restricted me to shoot at 1/100 second to eliminate screen flicker in my photos and videos. I'm using a Nikon D750 DSLR. Being limited to 1/100 made it nearly impossible to pull individual frames from my HD movies to display as images due to motion blur, and restricted my ability to change the speed to quickly adjust exposure.

I wanted to convert to 12V DC but wanted the option to return to AC at any time. I also wanted a full range of dimmer control after making the switch. I used power couplers like you would see on laptops and other electronics to make the new connections, and I've left a female connector on the currently-unused AC input which would allow me to switch back to AC on a moment's notice (I could have sent to the USA for a proprietary 4 prong plug that's used on the microscope, but instead opted to use these couplers). I required around 5 amps to operate the lamp, and discovered that a 12V DC 10A power brick would sustain between 6-7 amps (I first tried a 12V 5A power brick but it didn't work -- it only sustained about 3.3A). For dimming I'm using a US$3 PWM that has enough steps to give me very fine brightness control. I've added a switch on the box to bypass the dimmer and give 100% power to the lamp, which will be useful when I occasionally want to burn off some blackening if it builds up on the glass.

I'm running the bulb now at random voltages, using voltage along with camera ISO and speed to control exposure with no flicker. I set a quick custom white balance in-camera whenever I change any of those settings.

Attachments:

- photo of the power supply
- photo of the new control box
- schmatic of the electronics

Here is a short video that shows the new setup. At the end of the video I point to the female connector I've attached to the original AC plug (it's covered with electrical tape to keep it clean) which will allow me to return to AC power if I ever want to.

Attachments
dc power supply for microscope lamp.jpg
dc power supply for microscope lamp.jpg (133.22 KiB) Viewed 1311 times
dimmer box outside of box.jpg
dimmer box outside of box.jpg (129.34 KiB) Viewed 1311 times
12V DC dimmer box.png
12V DC dimmer box.png (74.82 KiB) Viewed 1311 times

Post Reply