Sunday, November 18, 2012

Dettol plunger pump test

Hi again,

I made a test using the Dettol plunger pump to deliver water to a becker. Using a balance, I determined the volume delivered. You can see the unmount process from my last post Dettol No Touch Tearsdown.

To control it, I cut the infrared led and I connected the anode of the LED to the emitter of a BC548 transistor and the cathode of the LED to the ground. The transistor was pulled-up to the 5V with a resistor of 510 ohm connected to the collector. To switch the transistor, I used a push-button pulled-up to 5V. The base of the transistor was connected between the resistor and the push-button. So, when I press the button, I simulate the hand cutting the infrared light beam. Only the supply power of the Arduino board was used with a prototype shield from Sparkfun. I did not change the electronic circuit inside of the pump because I wanted something simple to be controlled.

De Dettol infrared webcam

To confirm if the system was working, I used my webcam modified without the IR filter.

Dettol infrared webcam

The next video shows in detail the electronic parts and the wire that holds the IR LED.

The plastic parts that contact with solution is made of PP. It make it acceptable to acids and bases.

I used crystal PVC tubes of 1/8" and a 2cm of crystal PVC tube to make the connection with the inlet of the pump and two clamps (yellow and green).

A balance with 0.1g of precision was used to this test. Considering the density of the water is 1g/mL, the volume add each time that I press the button is 1.5mL. It is a huge volume for a fine titration. However, this pump could be useful for big volumes. One possible application could be use two pumps (one with an acid and other one with a base) to mount a pH-stat: a device that dose acid and base to maintain the pH constant.

If you have a suggestion, open the discussion.


Dettol No Touch Tearsdown


I have been thinking to mount an automatic titrator. The most important parts are the liquid pump and the flow meter. I wanted something cheap and easy to buy. But, it is not a easy task.

Once, I was in a cosmetics shop, not for me, and I saw a Dettol No Touch Hand Wash System for R$ 27,40, here in Brazil. I bought one to umount and remove the liquid pump.


I took some photos the unmount process. This is the link to the PicasaWeb album.



I am really impressed about the quality of the parts and the design of the project. All parts are labeled with the recycle code. The black parts and the external case (white and gray) are ABS and the  translucent parts are PP.

The pump is a plunger pump with two valves. When one is open, the other is closed. It works well when it is filled with liquid.

In a next post I will show the pump controlled by a switch to deliver volumes.