Print PDF
Favorite
Email
Step 5First Half of the Large Schematic, the LDR Sensor
The first half is the part of the circuit that sense whether or not the laser is on the LDR or not. The sensitivity can be dialed in with the 10K variable resistor. The only advice I can give you is to just play around with the variable resistor because the light levels will vary depending on where you put it.
Set up this half of the circuit on a bread board but leave out the relay, we are going to replace the relay with an LED for now.
TIP: I set mine as sensitive as I could; I then used a tube spray painted black to cover up the LDR to shield it from excess light. This way all I need to do is aim the laser down the tube and I can be sure that no light apart from the laser light will reach the LDR.
Before you throw the relay on, I have shown an LED in my schematic. Using the LED allows you to visually see the LDR working and how sensitive it is. This is how you should dial it in. Play around with the Variable resistor so that the LED lights up in almost complete darkness. When you turn the lights on, the LED should turn off. If you can get it to do this you are heading in the right direction. Next, get a family member, friend, or if you can manage yourself, cup your hand over the LDR, dont completely cover it, and shine the laser on the LDR. You should set it so that the LED is completely off when the laser is on the LED. When you move the Laser off the LDR which is still cupped in your hand, the LED should brightly light up. This means that you have set the correct sensitivity.
For a final test, if you are going to shield your LDR with a tube (I recommend it) put your LDR in it, line up the laser, and you should see that the LED is off. Walk through the laser and the LED should light up.
The next stage is to ditch the LED and replace it with a relay, but not yet!! Its best to understand what is going on in the second half of the circuit which is explained in the next step.
Set up this half of the circuit on a bread board but leave out the relay, we are going to replace the relay with an LED for now.
TIP: I set mine as sensitive as I could; I then used a tube spray painted black to cover up the LDR to shield it from excess light. This way all I need to do is aim the laser down the tube and I can be sure that no light apart from the laser light will reach the LDR.
Before you throw the relay on, I have shown an LED in my schematic. Using the LED allows you to visually see the LDR working and how sensitive it is. This is how you should dial it in. Play around with the Variable resistor so that the LED lights up in almost complete darkness. When you turn the lights on, the LED should turn off. If you can get it to do this you are heading in the right direction. Next, get a family member, friend, or if you can manage yourself, cup your hand over the LDR, dont completely cover it, and shine the laser on the LDR. You should set it so that the LED is completely off when the laser is on the LED. When you move the Laser off the LDR which is still cupped in your hand, the LED should brightly light up. This means that you have set the correct sensitivity.
For a final test, if you are going to shield your LDR with a tube (I recommend it) put your LDR in it, line up the laser, and you should see that the LED is off. Walk through the laser and the LED should light up.
The next stage is to ditch the LED and replace it with a relay, but not yet!! Its best to understand what is going on in the second half of the circuit which is explained in the next step.
| « Previous Step | Download PDFView All Steps | Next Step » |
 |
Add Comment
|
