Java Circuit Simulation Workaround ▾

Due to recent changes by Oracle, java applets have become difficult to run in the browser. To mitigate the troubles, Oracle has provided the following websites to help users troubleshoot: and

Even after following the above instructions, loading applets may still show warning concerning “unsigned application” and “unknown publisher”. For Teahlab in particular, these warnings are due to the fact that we have opted not to pay a third party such as Verisign to sign our applets. Any warning that comes up when you try to run our applets should emphasize that our applets will always run with “limited access”, which is Oracle’s way of letting you know that teahlab doesn’t do anything on your computer except running the circuits you see: in other words, our applets are safe to run.


The Teahlab Team

VIDEO TUTORIALS: The 4-Bit JK Flipflop Counter
by Isai Damier @isaidamier

Modulo16 means the counter goes through sixteen different states and so can count from 0 to 15. For each bit we use one JK flipflop and one AND gate. The reason this counter works is because JK flipflops toggle when both inputs are asserted (i.e. J=1, K=1). So, for example, on every cycle of the clock the least significant bit always toggles. The reason the other bits dont toggle has to do with the AND gates that are in the way. The output of an AND gate is asserted only when all the inputs are asserted. As a consequence for the counter, a bit will only toggle when all the less significant bits that precede it are asserted.