Upgrading Autofade Lamp Test Circuit

Well, today was kind of discouraging. Here’s the new autofade lamp test circuit, upgraded:

And here’s the key:

A: I replaced the red LED with a flashlight lamp. The soldering operation was successful and the light is bright enough.

B: I upgraded the capacitor from 1000 microfarads to 3300.

C: The transistor got hot, so I swapped out the 2N3904 to a 2N4401.

And . . . it doesn’t work.

When the LED is swapped back in, the circuit works fine, but there’s not enough base current to amplify the collector current enough to light the lamp. And I do mean that I don’t even see a glimmer.

Where to now? Try a power transistor, try two transistors in piggy-back, try different resistance values. I’m sure there’s a way to make this work, but we’ll probably put it aside for a while because I want to spend some time brainstorming ideas for other future products and how to market them.

Maybe I should draw something in Sketchup. That’s often relaxing.

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About engineerzero

Once and future engineer.
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2 Responses to Upgrading Autofade Lamp Test Circuit

  1. chocobo_rider says:

    How much volts require your flashlight lamp to turn on?

    • engineerzero says:

      The Radio Shack package doesn’t say. But the rated voltage is 2.33 volts and the rated current is 270 mA, if that helps. It’s a lamp type 243 and a bulb type GTL-3, if that helps.

      BTW, I got the thing to work. I’ll discuss on Monday.

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