Hi, guys welcome to Electrical Projects channel.
Today I will show you how to build a very unusual light bulb flasher, the unusual part
about this flasher that it doesn’t use any transistors, not even diodes,
therefore it is very simple. To build this device we'll need:
a 12V light bulb, a 12V relay, a 2200uF capacitor, a 100 Ohms resistor,
and wires, and of course, well need a power source to connect this device to.
In theory, that’s all we need, but I think it may be not that simple,
So maybe well need a couple more components, we’ll see.
Now we are ready to start building this device.
As always let’s have a look at the circuit diagram and let’s build this device according
to it.
First, let’s strip black and red wires, I am going to use these wire to power the device.
Let’s solder the red wire to the common pin of the relay.
Now let’s connect 2200uF capacitor to the coil leads of the relay, and let’s connect
100 Ohms resistor between “normally closed” contact of the relay and the coil lead of
the relay.
And it’s probably time to connect the black wire.
We need to connect it to the coil lead of the relay.
Now, let’s strip white and yellow wires, I’ll use these wire to connect a light bulb
to this device.
Now let’s connect the yellow wire to the “normally open” contact of the relay,
and let’s connect the white wire to the minus.
Now, let’s solder everything together.
Now, let’s strip the white and yellow wires from the other side….
and let’s solder them to the light bulb.
In theory, it should work… let’s test it…
And as you can see at first it worked but then it stopped working… it is not very stable…
Now it blinks when I hit the relay…
Do you know why doesn’t it work properly?
Stop the video and think for a while… what is wrong?…
Ready for the answer: well, the problem with the relay.
But if you test this relay yourself will not find anything wrong with it...
How is it possible?
Well, let me explain.
As you can see the electric current flows through the normally closed contents, then
through resistor, and charges the capacitor C1, when the capacitor charges the voltage
on the coil becomes higher and higher.
So we expect that at some point, when the voltage will be high enough the relay will
switch, and disconnect the power to coil.
But that is not what happens here, at least not with this relay.
What actually happens here is that when voltage on the coil rises, the normally closed contact
became worse and worse at conducting electricity, so we have “a poor electrical connection” here.
And that doesn’t allow the capacitor to fully charge and prevents the relay from switching.
Well, after thinking about how we can overcome this problem, I came up with an idea, I decided
to add to this circuit sequentially connected resistor and capacitor and connect them to
the normally closed contacts.
Let’s try it.
Let’s connect 10 Ohms resistor and 470uF capacitor.
Now let’s test it.
As you can see, now it’s working much better,
but then when I adjusted the voltage it stopped working at all,
then after some time it started to work again…
I don’t know what exactly is going on, but I think we still have a problem with that contact…
well, trying to make it more stable I decided to connect a bigger capacitor.
I must say that at first, it did not work very well, but then it became pretty stable.
Now let’s try to connect it to a 12V battery.
It works…
Right now it works very well.
Well, Let’s sum it up: can we build light bulb flasher without any transistors?
The answer: Yes, defiantly.
Will it be stable?
Well, it depends.
It will not work well with some of the relays, but it may perfectly work with other relays.
To make it work with some of the relays, you will need to connect a capacitor with a resistor
to make it work.
And that is all for today, I hope you liked this simple project, if so don’t forget
to like this video and subscribe.
Thanks for watching, see you next time!