haroldjclements
- Oct 17, 2013
- 24
- Joined
- Oct 17, 2013
- Messages
- 24
Hello forum,
I am after some education on using a Transistor as a switch. I have read a few help/tutorials pages, but I am just not getting it.
If you take the diagram below; this works exactly as I would expect. When there is a positive voltage on the base of the transistor, the switch is close allow the current and voltage flow from Vcc through the LED, Resistor, into the Collector, out the Emitter to ground. When no voltage is applied to the base, the no current is allowed to pass through the Collector to the Emitter. - As an extremely elementary explanation, I am happy with this.
However, I would have throught that the same would be true if I reversed the position of the LED.
I don't understand why when a positive voltage is applied to base that the 5v does not flow from Collector to Emitter, thus light the LED - and act like a switch as per the first diagram above.
Any basic layman's explanation would be gratefully received.
In my example, I have used a single LED and a (slightly depleted) AA battery supplying the base current in my example, but the problem that I was trying to solve was that I have a common cathode RGB LED that is being controlled by PWM using an ESP8266, and I was hoping to repeat this circuit three times with three different pin-outs on the ESP connected to the base of the transistors.
Thanks in advance for your help,
Harold Clements
I am after some education on using a Transistor as a switch. I have read a few help/tutorials pages, but I am just not getting it.
If you take the diagram below; this works exactly as I would expect. When there is a positive voltage on the base of the transistor, the switch is close allow the current and voltage flow from Vcc through the LED, Resistor, into the Collector, out the Emitter to ground. When no voltage is applied to the base, the no current is allowed to pass through the Collector to the Emitter. - As an extremely elementary explanation, I am happy with this.
However, I would have throught that the same would be true if I reversed the position of the LED.
I don't understand why when a positive voltage is applied to base that the 5v does not flow from Collector to Emitter, thus light the LED - and act like a switch as per the first diagram above.
Any basic layman's explanation would be gratefully received.
In my example, I have used a single LED and a (slightly depleted) AA battery supplying the base current in my example, but the problem that I was trying to solve was that I have a common cathode RGB LED that is being controlled by PWM using an ESP8266, and I was hoping to repeat this circuit three times with three different pin-outs on the ESP connected to the base of the transistors.
Thanks in advance for your help,
Harold Clements
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