Hi, guys, welcome to Electrical Projects channel, today I’ll show you how to build a simple
delay timer.
With such timer you’ll be able to turn a light bulb or any other appliances on or off,
for a defined period of time.
To build such timer and demonstrate how it works I am going to use: 2n7000 MOSFET, a
button, 100 Ohms resistor, 470 k resistor, 47uF capacitor, 12V relay, and a 1N4007 diode.
To test how it works I’ll use a piece of 12 V LED strip, but it can be replaced with
a light bulb for example, I’ll show it later.
And of course we’ll need some wires.
To power the circuit I’ll use 12V DC power supply.
On the left you can see the schematic for this project, so let’s start soldering accordingly.
First let’s solder the diode to the coil leads of the relay,
Now let’s solder drain lead of the MOSFET to the anode lead of the diode.
After it is done, let’s connect together 47uF capacitor and 470k resistor,
Also, let’s connect a wire to the positive lead of the capacitor, this wire later will be connected to the button.
Now let’s solder the wire and the positive lead of the capacitor to the gate lead of the MOSFET.
After it is done lets connect a black wire to the negative lead of the capacitor and
then solder it to the source lead of the MOSFET.
Now lets solder a yellow wire to 100 Ohms resistor
Also, let's connect a red wire to another lead of the resistor,
now let's solder it to the diode and the coil lead of the relay.
And now it is time to connect a button…
Lets test this button to make sure that it works, also this test helps to understand
how to connect the button.
Ok, the button works, so let’s strip yellow and blue wires and connect them to the button,
and after a little bit of soldering this device is almost ready,
Now we just need to solder wires to the LED strip.
Now let’s connect the LED strip to negative wire and to the “normally open contacts”.
And now we left with the last wire… we need to connect it to common lead of the relay
and to the positive wire.
And it is ready, it is time to test it.
Testing is pretty strait forward, we just need to connect it to a 12V DC power supply
and press the button.
Also let’s measure time, in order to find out how long the LED stays on.
With current resistor and capacitor values it is around 38 seconds.
The cool thing about using relay that you can control almost any device…
Now I am going to connect 230 volt light bulb and power it from mains electricity.
It is kind of dangerous, so I don’t recommend trying.
I just want to show you that it’s possible.
Also it is easy to change the amount of time that bulb stays on, you can do it by changing
the resistor or capacitor values, for example you can use 470uF capacitor instead of 47uF,
and this device will stay on 10 times longer.
And as you can see it works with the light bulb as well.
And that is all for today, thanks for watching, see you next time!