Dried Seed Timer by the Jolly Roger

A time delay device for electrical firing circuits can be made using

the principle of expansion of dried seeds.


Material Required:



Dried peas, beans, or oter dehydrated seeds

Wide-mouth glass jar with non-metal cap

Two screws or bolts

Thin metal plate

Hand drill





1) Determine the rate of the rise of the dried seeds selected. This is

necessary to determine the delay time of the timer.

a) Place a sample of the dried seeds in the jar and cover with


b) Measure the time it takes for the seeds to rise a given height.

Most dried seeds increase 50% in one to two hours.

2) Cut a disc from thin metal plate. Disc should fit loosely inside the



NOTE: If metal is painted, rusty, or otherwise coated, it must be scraped

or sanded to obtain a clean metal surface


3) Drill two holes in the cap of the jar about 2 inches apart. Diameter

of holes should be such that screws or bolts will thread tightly into

them. If the jar has a metal cap or no cap, a piece of wood or plastic

(NOT METAL) can be used as a cover.

4) Turn the two screws or bolts through the holes in the cap. Bolts

should extend about one in. (2 1/2 cm) into the jar.


IMPORTANT: Both bolts must extend the same distance below the container



5) Pour dried seeds into the container. The level will depend upon the

previously measured rise time and the desired delay.

6) Place the metal disc in the jar on top of the seeds.


How to use:



1) Add just enough water to completely cover the seeds and place the cap

on the jar.

2) Attach connecting wires from the firing circuit to the two screws on

the cap.


Expansion of the seeds will raise the metal disc until it contacts the

screws and closes the circuit.