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| rgb_dimmer [2015/02/22 20:11] – [Recommended LED module and resistors] breaker27 | rgb_dimmer [2023/02/28 13:49] – breaker27 |
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| The "normal" resistors are enough if you use a thin glass housing (as shown on the homepage). You can use normal 1/4 W resistors and the LED module won't heat up much. No heat sink required. This is the safest and easiest choice. | The "normal" resistors are enough if you use a thin glass housing (as shown on the homepage). You can use normal 1/4 W resistors and the LED module won't heat up much. No heat sink required. This is the safest and easiest choice. |
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| The "bright" resistors result in LED currents of ~120mA and a power dissipation at the LED module of ~1W. It should not need an additional heat sink, but it gets hot already (you can touch it, maybe ~50°C). The resisors have a calculated power dissipation of ~0,3W. 1/4W resistors max be enough, but I recommend to use metal film resistors (1W). The overall current of the RGB dimmer is 380mA, so a typical power supply for smartphones with 500mA max. current fits perfectly. | The "bright" resistors result in LED currents of ~120mA and a power dissipation at the LED module of ~1W. It should not need an additional heat sink, but it gets hot already (you can touch it, maybe ~50°C). The resisors have a calculated power dissipation of ~0,3W. 1/4W resistors max be enough, but I recommend to use metal oxyde resistors (1W). The overall current of the RGB dimmer is 380mA, so a typical power supply for smartphones with 500mA max. current fits perfectly. |
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| For the "max" resistors, you need an extra heat sink at the LED module and resistors which can cope with the higher current (1W). | With the "max" resistors, you definitely need an extra heat sink at the LED module and resistors which can cope with the higher current (1W). |
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| Use resistors which can tolerate the power they consume. The power is calculated as: | Use resistors which can tolerate the power they consume. The power is calculated as: |
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| with U_Res the voltage at the resistor. | with U_Res the voltage at the resistor. |
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| | ===== Modification of PCB rev. <= 1.1 ===== |
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| | The older PCBs have the speaker connected to PD3 (pin5). Since the 16 bit timer has to be used to generate accurate frequencies, you have to connect it instead to PB1 (pin 15). |
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| | The pin to drive the transistor for the blue LED has to be moved from PB1 (pin 15) to PD3 (pin 5). |
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| | In future PCB versions, this shall be changed in the schematic and layout. |
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| | To perform the modification, cut the PCB tracks on the marked positions and connect them to the other pins. |
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