#### mona

Joined Aug 24, 2008
3
In the circuit of digital radar speedometer what is the laser diode used?Any specification for that?Can any alternatives be made if it is not found?

#### SgtWookie

Joined Jul 17, 2007
22,226
I have no clue what you are talking about.

Do you have a link to the schematic or project?

It seems to me that there was a thread many months ago about such a project. With the components specified in the schematic, and the unrealistic specifications for operation, the project would not have been very practical even if there were any chance at all of it working.

#### jpanhalt

Joined Jan 18, 2008
11,088
As suggested, if you can give a bit more information, it would help.

First, remember that laser speed detection is based on two measurements of position, not doppler shift as is used with radar.

So, you need a short pulse. The pulse length in the inexpensive laser distance devices (e.g., Stanley Fat Max) is around 1 nS. As far as I know, the devices cannot be repeatedly triggered very rapidly, but you could trigger two devices sequentially very closely and use those results.

Another problem will be range. What type of range do you need? The FatMax series go to a maximum of 600'; the cheaper models are limited to 100'.

John

#### mona

Joined Aug 24, 2008
3
http://www.electronics-lab.com/projects/test/021/index.html. this site provides the schematic of the citcuit that i'm talking about. is the probability of the success of that circuit very less?i have one more circuit doppler radar speedometer. the link is given below
http://www.circuitcellar.com/microchip2007/winners/DE/MT1623.html.
this circuit look more likely to be a succesful on . but i could not find all components.those parts mentioned as bonus parts i could not find them. can u suggest any alternatives?
reply needed as soon as possible.

#### SgtWookie

Joined Jul 17, 2007
22,226
The first link is someone's dream. It doesn't even qualify as a radar. "Lidar", perhaps. RADAR is an acronym for "Radio Detection And Ranging". If it doesn't involve electromagnetic waves travelling through the air, it can't be a RADAR.

The 2nd link - well, many of the parts will be inexpensive. However, the radar portion will be quite expensive; perhaps a few thousand dollars. Can't give you a source offhand. I suggest that you write an E-mail to the author; he knows where he bought his parts.

The "Bonus Parts" are available from Microchip. However, they are not needed for this project. The sponsor, Microchip, would just have liked to have people feature more of their products in a solution.

#### jpanhalt

Joined Jan 18, 2008
11,088
I have yet to tear into my FatMax. It is too much fun to play with to disassemble right now. They can be had for about $50 new on eBay (That's where I got mine). If you are interested in "playing" with time of flight laser measurements, you might consider starting with such a device. John #### jpanhalt Joined Jan 18, 2008 11,088 Here are some added thoughts: 1) Remember the Hot Wheels radar gun? It's now available for about$10 on eBay. Here is one.

2) Search eBay for "radar speed -detector". I got 70 items, many of which are true radar guns for a lot less than \$100. Here is one example.

John