• Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

PLL?

Status
Not open for further replies.

akg

New Member
erique82 said:
Yeah, you are right. But what do you mean by "going digital" from the beginning? are they any other easier means to achieve distance measurement by laser? Besides triangulation method, of course. That's rather too simple.
as he explained earlier , laser diode cannot be analog modulated , u can only on or off it (digital modulation), and then whole ckt to be digital so make it work at full speed .(DAC takes time )
 

evandude

New Member
akg said:
as he explained earlier , laser diode cannot be analog modulated , u can only on or off it (digital modulation), and then whole ckt to be digital so make it work at full speed .(DAC takes time )
Actually, the laser audio transmitter I referenced in my previous post WAS done with analog modulation. As I mentioned, to do that requires careful selection of the Q-point of the modulating transistor, and amplitude of the modulating signal... but think about it, when you design, say, a transistor audio amplifier, you set a Q-point and as long as the signal amplitude is small enough, the behavior is approximately linear. Same thing applies to the laser diode. You will just have to have decent amplification and filtering on the receiving end to compensate for the small modulation amplitude.

Analog modulation of the laser may not be perfect, but I've heard that audio transmitter, and the audio wasn't terrible, so I know it's at least possible :lol:
 

Russlk

New Member
The usual method is to pulse the laser and measure the time required to receive the reflection. If you feed the transmitted pulse and received pulse into an XOR, as shown below, and filter the XOR output to DC, then feed the DC to a DVM, you can get the distance with minimum trouble.
 

Attachments

Status
Not open for further replies.

EE World Online Articles

Loading

 
Top