Virucidal Oven

Virucidal means - having the capacity to or tending to destroy or inactivate viruses. In this project, I am using an out of order old microwave oven to make a very simple DIY ‘disinfector’ device to destroy or inactivate viruses, intended mostly for the CORONA virus. The main weapon is the UVC germicidal light which is used instead of the Magnetron of the Microwave Oven.

What’s the difference?? Nothing special!!!! Well – the answer is ‘simplicity’

There are lots of examples and designs of disinfector ovens using UVC light to destroy the virus. I am not going into the detail of the mechanism of how UVC [258 nm] light can effectively act as a disinfector in this blog.

Here, My goal is to make a very simplified version of the device where I can make it easier DIY so that anyone can do it with basic electrical knowledge without taking the headache of designing complex circuitry for exposure time control and safety lock etc.

So, it has to be a solution which is -

Efficient

Low cost

Easy to setup

And SAFE

And the automatic choice for me is a MICROWAVE OVEN!!!

I used my old microwave oven which has a burned out magnetron. It was from a local brand ‘RANGS’. They are the official dealer of SONY in Bangladesh. The build quality of the microwave oven is superb. I just placed a germicidal UVC light from PHILIPS at the terminals of the magnetron.

Advantage: it almost has all the basic requirements –

• The basic timing circuits are built-in
• There are safety locks for doors
• The turn table helps to distribute the UVC exposure evenly
• Stainless steel inner body to avoid any degradation
• Glass on the front door gives the visibility but prevents UVC to pass through
• Only a germicidal UVC tube and ready-made driver circuit is needed

Assembly:

Step01- I removed the magnetron and other unnecessary parts from the chassis. I removed the top cover and drilled two holes to mount the T8 tube holders.

Step02- I placed the wires with heat shrink tubes. Because the insulation of the wires can be degraded due to UVC exposure for a long time. However, the tube holders are also made of plastic, but the intensity of the UVC light is almost nill at the edges. It is highest at the middle for the lamp tube.

Step03- I connected a driver for the UVC lamp at the terminals of the magnetron. I had to drill some holes and placed connectors for a neat assembly of the cables. The general purpose bulb was missing!! I can’t remember where it had gone. So, I had to mount another bulb separately so that I can see the internal staffs while it’s operating.

Interior:

Operation:

Just like a traditional microwave oven, the exposure time can be varied accordingly. However, other options are disabled and there is no control over the power or intensity of the exposure. Once the door is locked and time is fixed, the UVC lamp turns on with pressing the start button. A fading blue light is visible from outside through the glass front door.

There are two limitations of this simple design. The UVC is exposed only from the top. Several other lamps can be placed on the side walls too to overcome this limitation.

The turntable side does not get any exposure, as UVC does not reflects back from the metal body with much energy. So, the stuffs placed inside need to be flipped manually after the first session of exposure.

**there is an interesting observation. I have a screen cover attached on the display of my phone. It had a crack previously. After a month of UVC exposure on regular basis, I noticed several cracks on the cover and the paints on the plastic body at the back became more brittle.

Overall, this is a very low cost solution. Easy to build and quite effective. I am using it from July 2020. It was fun to utilize the old oven and recycle it for some other purpose. As it goes with this project14 theme, I thought better to share it with you all.

Hope you all enjoyed it.

Thanks.