The notes below are outline notes based on information obtained from a variety of sources.     I have listed the relevant european standards.  The notes on this page have not yet been checked against the standards.    It is recommended that for final detail design, reference is made to the standards.

BS EN 894-1:1997 :Safety of machinery. Ergonomics requirements for the design of displays and control actuators. General principles for human interactions with displays and control actuators
BS EN 894-2:1997: Safety of machinery. Ergonomics requirements for the design of displays and control actuators. Displays
BS EN 894-3:2000: Safety of machinery. Ergonomics requirements for the design of displays and control actuators. Control actuators
BS EN 894-4:2010: Safety of machinery. Ergonomics requirements for design of displays and control actuators. Location and arrangement of displays and control actuators

Below are list suggested for sizes of letter and symbols to be used on controls and machines used in well illuminated areas..
Black letters against white background are clearer to read in normal daylight conditions.   In relatively dark conditions white letters on a dark background are better.

Rotary Controls.. The accepted direction for rotary controls is Clockwise motion of control to increase the variable. Anti-clockwise motion to decrease the variable...

In direction controls Anti-clockwise motion results in a turn to the left in forward motion and clockwise motion result in turning to the right in forward motion..

Lever controls.. The accepted direction for linear controls is movement forward,to right or up to increase variable and movement towards you, to left or down to reduce variable...

A push button can be arranged for operation by finger or by hand..
Suggested dimensions..

Toggle switches should only have two positions "on" and "off" they should preferably be located on vertical panels with vertical toggle motion.
The angle of motion should be about 45^o
Diameter.. 3 - 25mm
The length..12- 50mm
Resistance to movement..2.5 - 15N

Large levers are sometimes used where significant operating forces are required.
Maximum forward and back motion 90^ototal.
Maximum forward and back motion 350mm total.
Maximum lateral motion 45^o total.
Maximum lateral motion 150mm total.
Maximum operating force 130N forward and back.
Maximum operating force 90N sideways.

Rotating knobs provide a convenient method of controlling variables.  They should conveniently fit the hand , be easy to rotate, and should not impair viewing.

Two options are available knobs 1) Rotating Switches with indented motion (click stops) and 2) continuous motion knobs.

Rotating Switches.
Successive positions should not be less than 15^o apart if the knobs are controlled by a pointer in view.
Successive positions should not be less than 30^o apart if the knobs are controlled by a feel.

Suggested Design Parameter.

Continuous Motion Knobs
Continuous motion knobs allow precise regulation and allow control using finger or hand grip i.e delicate movement or rough movement..

Suggested design parameters

Arrow shaped , pointed bar knobs allow settings to be made quickly and conveniently...

Suggested design parameters

Handwheels allow large forces to be applied because two hands can be used and gearing can be included for slow movement.

Suggested design parameters

Rotating cranked wheels allow for operating of machines over long movements using continuous rotation of the crank.    The gearing between the crank and the motion may be fine or coarse and may be switched between ratios.   A crank handle allows fast motion and the handwheel can be used for more precise motion.

Suggested design parameters

These sketches are very dated and should only be used for general guidance