I tried with 5V to turn on a status LED and a lamp/a 5V pump with two NPN transistors. Ofc at first as simulation. I'm new to simulations so maybe I'm missing something.

In easyEDA it does not turn on the bulb/pump-fake: enter image description here

But in two other simulation software everything works like a charm: enter image description here

Am I doing something wrong in easyEDA? Would be very hard if I can't trust that software to do my PCBs later...

So the overall question: Am I the error, or easyEDA?

Thanks for your help!

Changed the bulb with an resistor: enter image description here

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    \$\begingroup\$ Are those symbols accompanied by their own models or subcircuits? Because, if they're only "cosmetic" (e.g. for PCB) then chances are that they simply cannot simulate. \$\endgroup\$ Commented Dec 1, 2022 at 18:58
  • \$\begingroup\$ I used all items directly from easyEDA without any custom content or something else if you mean that. easyEDA has the "simulation mode" where this light bulb is added for simulations. If I add it directly between VCC and GND it turns on when I hit "play" \$\endgroup\$
    – dessi
    Commented Dec 1, 2022 at 19:01
  • \$\begingroup\$ Then maybe the switch needs a setting? Is it NC or NO? \$\endgroup\$ Commented Dec 1, 2022 at 19:02
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    \$\begingroup\$ Use a resistor, see if that works. If it does then chances are that the bulb is fishy. \$\endgroup\$ Commented Dec 1, 2022 at 19:06
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    \$\begingroup\$ Yes, it looks saturated, so the bulb should have lit up. The only other thing can think of is that maybe the bulb, itself, has some settings, maybe it's set for 12 V, or 24 V, and it has a check for voltage. I don't know. But theevidence seems to point at the bulb (unless it's something else I have overlooked). \$\endgroup\$ Commented Dec 1, 2022 at 20:09

1 Answer 1


Feeding more than one parallel base-emitter junction from a single resistor leaves the distribution of current to chance, variations in device and environmental parameters.

About 80 mA of base current is a bit high even for the 200 mA lamp - say 220 Ohms there, 2k2 for the "LED transistor".

The paranoid add a resistor from base to emitter - about 2 to 10 times "the base resistor" is a start.


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