Lights and Display Board Circuits

Bicycle Light With Afterglow Schematic Circuit Diagram

Delayed Turn-Off for Bicycle Lights

This design guarantees that the bicycle light continues to function for a brief duration even after the bicycle (and consequently, the dynamo) has halted. However, a drawback is that the bike’s frame cannot serve as the common return path. An additional wire must be installed for this purpose. This necessity arises due to the utilization of a bridge rectifier. Ensuring full-wave rectification of the dynamo voltage. Consequently, the alternating and direct voltages must remain isolated from each other.

Sustained Illumination After Bike Stops

The circuit is engineered to keep the bicycle lights operational for a short time after the bicycle (and thereby the dynamo) has come to a halt. The drawback here is the inability to use the bike’s frame as the common return: a separate wire has to be integrated for this purpose. This requirement arises because a bridge rectifier is employed to achieve full-wave rectification of the dynamo voltage. This setup mandates isolation between the alternating and direct voltages.

Bicycle light with afterglow Schematic diagram

Charging the NiCd Battery and Powering Bicycle Lights

In this configuration, bridge rectifiers are employed, sharing one half. Diodes D1 to D4, along with R5, create the bridge through which the NiCd battery gets charged while the bicycle is in motion and the dynamo is connected. Additionally, diodes D1, D3, D6, and D7 establish another bridge that powers the bicycle lights when the dynamo voltage reaches a certain level.

Dynamo Operation and Power Supply Switching

As the dynamo operates, capacitor C1 is charged via D5, leading to the conduction of transistor T1. When T1 conducts and the dynamo output falls below a specific threshold, T2 is triggered. This action powers the bicycle lights using the stored energy from the NiCd battery.

Bicycle Standstill and Disconnection

During bicycle standstill when the dynamo ceases operation, C1 no longer charges. Consequently, T1 gradually ceases conduction, subsequently switching off T2. This event results in the bicycle lights turning off as well.

Preventing Battery Discharge

To prevent slow discharge of the NiCd battery through the circuit when the bicycle is not in use, switch S1 is incorporated. When not in use, the switch should be opened to avoid unnecessary battery drainage. If the duration of afterglow is deemed insufficient, increasing the value of C1 will extend the time the lights remain illuminated.

 

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