ARDUINO, DIY, Electronics, Inspiring, LEDs, photography, Raspberry Pi, Robotics

Experiments with a Light Meter

Why I am interested in Light meters?

When I was working in Scotland, I came across photo dynamic therapy (PDT), which uses light sensitive drugs to kill cancer cells. In the entire UK, there are only two PDT centers (afaik), one of which is in Dundee. By visiting the PDT center in Dundee, I realised that after applying the PDT drugs, doctors ask patients to wait in  sun light for two hours. There is no particular reason for exactly two hours of exposure to sun light. Therefore, it is not possible to know how much light dose has been received by the patients. To address this problem, PDT center at Dundee measured sunlight across the UK and Ireland and suggested that  cheap lux meters can be used to measure the required lux dose. I met with one of the PI and discussed about this in detail.

The problem with cheap light meters:

However, most commercially available cheap lux meters can only give instantaneous measure of light. These are originally developed for photographers to know lighting in their photo and building mangers to know lighting in a room. But PDT application  requires the lux values to be logged, aggregated to know whether the required light dose is reached. I think the only way to realise that is through connecting the lux meters to a microcontroller and stream the values to a smartphone. For that I am going to use a cheap lux meter that I can confidently modify after reading this blog post .

What I did:

I ordered the lux meter with a brand name “Ceto”from the same vendor as suggested in the blog post mentioned above. I identified the pins required to tap to get the lux values out. These are the pins on the amplifier. I soldered wires to these pins to read the voltage. So effectively LUX values are converted to voltage values in this lux meter. For example LUX of 290 is converted as 0.288V. I connected these wires to a multimeter to  see these voltage values.


Guts of the LUX meter


Zooming inside


Red wire is signal


Black wire is ground


Hot glue to keep the wires in place


Made a hole to the case to let the soldered wires come out, so that I can feed them into a multimeter


More hot glue to fix the wires to the case


Connected the wires to multimeter and we can see the light values appearing on the Multimeter as voltage values.

In the next step, I will connect the lux meter to a Arduino Uno and Bluetooth so that its possible to record the  aggregated lux values overtime time to determine the light dose for PDT treatment. I will write these details in another post.

P.S: It is just one of my hobby project, not related to my research.

DIY, Electronics, Inspiring, Robotics

DIY Toy Centrifuge

Why I like a centrifuge?

Whenever I see a motor, I think why shouldn’t it be converted as a centrifuge. I like centrifuge as a scientific instrument, especially after seeing Lab on DVD systems to diagnose diseases. Recently, I came across Manu Prakash’s paperfuge, where whirligig/buzzer toy was modified to get high speed centrifuge without using any electricity. Although, I like the idea, it still takes more than 15 minutes to separate blood to any useful analysis such as malaria detection.  May be there are better ways to improve the existing technology to get a better centrifuge, a cost effective, functional, may be little bit funny one. Latest open source models use brushless motors used in drones to make a centrifuge. I would like to try that idea. However, one has to spend at least spend $30 to make such open source centrifuge. I would like to make a low-cost, fun toy type centrifuge, so that we can teach kids about centrifuges without spending so much.

How I made One:

I took a brushless DC motor from a CPU cooling fan and attached a conical shape of plastic that I cut from a water bottle. It looks good, I am getting decent speeds with a power bank or a computer USB. Look at the videos, where I tried to separate milk, which is not possible with this toy centrifuge. I am sure that we can separate some suspension solutions which I will try soon. So far the plus points of my design are that it doesn’t require any soldering, 3D-printing. I am planning to enclose it in a cardboard box for safety reasons, although current version doesn’t spin at high speeds to make any damage.


Top part of a water bottel


Attach the cap to a PC fan


Glue to attach the cap


Finally, PC centrifuge is here

Future Plans

I am trying to make a centrifuge that can go up to 16,000 rpm, with a system similar to the above. I already designed a 3D printed holder for tubes. I will update about it soon. Until then enjoy the footage of toy centrifuge video.