# Running lights on relay

Original author: Hamuro
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If you previously collected running lights on transistors, thyristors, or microcircuits, you might be interested in realizing the same effect on a relay.

Each of the three relays in this circuit is supplemented with an RC circuit providing a delay, as well as an OR diode for control from two places. One of the inputs of each diode "OR" is connected to the load of the previous relay, the other to the load of its own. Thus, having received a delayed response signal from the previous relay and having tripped, the relay will self-lock, which is equivalent to the input S of the RS-flip-flop.

Each of these “triggers” has an input / R - the upper output of the winding. Relay release occurs when this pin is connected to a common wire. A short circuit does not happen, because the current is limited by the resistors of the RC circuits. In the world of relay logic, pull-up resistors are also found. If the signal S for each “trigger” comes from the previous relay, then the signal / R - from the next.

Immediately after switching on, the circuit does not work, since there is no logical unit at the inputs of S of all three “triggers”. Button S2 is used to start running lights, button S1 is used to stop.

Resistors of RC circuits are selected by the formula:

U relay / U pit = R rpm / (R rm + R ogre ), where:

Urelay - rated voltage of the relay winding, V
U pit - supply voltage, V
R rm - winding resistance, Ohm
R ogre - resistor of the RC chain (desired), Ohm

The resistor power is selected with some margin based on the fact that it is tightening, and when the signal / R is applied, the total supply voltage minus the voltage drop across the diode is applied to it. To set the switching speed, you can select the capacitors of the RC circuits. Device in action: