A project log for Histology Tissue Processor

Cheap hackable tissue processor suitable for third world or citizen science hackers.

sgall17asgall17a 06/18/2020 at 00:460 Comments

1.   I have made a processing station out of wood with 5 bottles, 5 servos, and a magnetic mixer.  Magnetic mixer works well.

2.  Change of plan for the pinch valves.  I decided to use fewer and smaller 3D printed parts.  Printing big parts is slow,  making changes tedious, so I moved to make more use of wood and aluminium.   The servos are screwed to a wooden bar.  An aluminium bar is fixed beside the servo as "anvil" for  the cam to press against.  I will probably just use polymorph to hold the silicone hoses in place.

The servo horn has been changed from a helical cam to a straight horn. 

3.  3D printed joiners.   I only have 1m of 6mm od, 4mm id silicone tube and think I will need about 3-4m.  The tubing is fairly expensive to buy in Australia and very slow to bring in from China so I am only going to use silicone tubing in the pinch valve  and use clear vinyl tubing elsewhere.  This will not affect function.  All silicone tubing would be cleaner and more aesthetic.  I order to to this I printed 10 joiners to connect the vinyl to silicone.

3. Second air pump did not work.  I had ordered a second air pump a while ago from China.  Sadly it did not work,  (being open circuit)  so I did a destructive autopsy.  The problem seemed to be the  flimsy metal coated plastic brushes.   Another one ordered (bit more expensive this time).

4.   Servo connector.  I made a "dead bug" style servo connector for 8 servos.  For the  power leads I   soldered a thin wire along a row of 9 pins (two rows).  For the control leads I joined two rows of 8 pins by thin wire,  then glued all 4 rows together with epoxy.  I soldered a row of 8 female headers to some rainbow cable for the connector for the Arduino 2560 Mega.  This is compact, seems strong and tests out OK with a multimeter.  


 Test new servo valves.

Test sero connector.