How to use a PIR motion sensor to light up a 3.8 VDC bulb using battery and relay

Question

I would like to detect motion to turn off my 3.8 V, 0.3 A DC light bulb using a PIR motion sensor.

Recently I tried to connect it to a 5 V relay, Arduino Uno, and two 3.7 V Li-ion batteries, and the bulb seemed to burn out.

Any ideas on what should I do to my circuit, and what values of battery I need? Or should I put in a resistor instead?

I tried to modify the schematic with battery and DC light bulb referring to the schematic from here:

enter image description here

Do you have a 5V battery? Why do you need 2 x 3.7V batteries? Can you manually draw the schematic of what you wired and upload a photograph? — vu2nan, May 28, 2020 at 9:25
Thank you so much for the schematic. Sorry but does 5v battery exists? I can't seem to find any. — Aween Rozmi, May 30, 2020 at 0:59

vu2nan · Accepted Answer · 2020-05-28 10:24:19Z

0

Here's the schematic.

A 3.9Ω 1W voltage-dropping resistor is used in series with the 3.8V bulb.

answered May 28, 2020 at 10:09

vu2nan

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\$\begingroup\$ For the relay, do we connect it to no or nc? Because I want to turn off the bulb when the pir detect the motion. \$\endgroup\$
– Aween Rozmi
Jun 13, 2020 at 9:14
\$\begingroup\$ Hi Aween, 'NO' contact is shown. To turn off the bulb with the signal, you would need to wire the 'NC' contact. \$\endgroup\$
– vu2nan
Jun 13, 2020 at 9:39
\$\begingroup\$ Hi Aween, Is my answer acceptable to you? \$\endgroup\$
– vu2nan
Jun 26, 2020 at 6:32

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