User:Pranav Rathi/Notebook/OT/2012/05/21/pH-rocker for DNA-sequencing experiments

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Revision as of 17:15, 26 January 2013 by Pranav Rathi (talk | contribs) (Design)
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Design and Construction

Design and construction of the rocker is easy. It is one of the easiest things I made. I have completed all the work within 5 hours.


Most of the components were available in my lab. Some i bought. The slide show has all the parts with part number and company.

pH-rocker stand

  • 1 X MB6 thorlabs brad board
  • 2 X TR12-thorlabs posts
  • 1 X PH4 post holder
  • 1 X CL6-thorlabs clamp
  • Some 1/4 inch screws

Motor arm

  • 1 X PK22G21-Hennkwell 12V high-torque planetary gear motor
  • 1 X CP0@T-thorlabs cage plate
  • 1 X TR6-thorlabs post
  • 1 X RA90-thorlabs post clamp
  • 1 X black disk (salvaged from a radio)
  • 1 X ER1-thorlabs 1 inch cage rod
  • 2 plastic wire holders and 2 rubber cushions
  • some 8/32 and 4/40 screws

Power supply

  • Powerline variable DC-power supply from

pH sensor

  • PH37-SS Hach company pH sensor

Well plate

  • 96 Well plate for DNA-sequencing


The design is very simple. It is required for good stable results that pH sensor is moved in circular motion in the well as what used to be done by hand. So basically I am simulating the circular motion of hand by using a high-torque motor. The sensor wire is pretty stiff so high-torque motor is useful to get smooth circular motion.

For 96 well plate it is important that the arm can be adjusted to cover the whole well plate; this is achieved by adjusting the angle, height and length of the arm by 90o clamp. The rocker can be used with any DC-variable power supply (I bought the power supply from Amazon for $15), which can also let choose different speeds.

I designed the rocker such that most of the tools and hardware are available in my lab with least machining.