SPEED TRAP

    

This was designed for a radio controlled car track using cars of 1/10 scale. It works by measuring the time it takes for an object to pass 2 sensors placed exactly 200mm apart. In this way the speed can be calculated in "MPH" and ms-1.

In fact 2 versions were made with the second designed exactly the same but the case was designed for indoor use.  

Designed and built by Phil Townshend 2008

The principle is simple. Take the time it takes to travel 200mm, multiply this by 5 to get the time for 1 metre then take the reciprocal.
eg: Time taken to pass 200mm = 0.1s. Then 1 metre takes 5 x 0.1 = 0.5s,
so speed = 1 / 0.5 = 2 m/s.
The speed is displayed in metres/second by default, but pressing SW2 will display the speed in MPH but at a scale speed so actually it will read 10x as much. 
The Math routines I wrote I am very pleased with. They can multiply 16bit by 8 bit numbers and are based on long division and multiplication. I wrote them myself - honest!!

The sensors used were opto-transistors and the light sources were some 1mW keyring laser pointers (I found a deal on 30 for £10 from Japan - free shipping - bargain!) The lasers and sensors were positioned such that a beams were directed across the track exactly 200mm apart. The cars would break the beams as they drove past.

Boxes were made up from 6mm MDF to protect the sensors and Laser modules and also to ensure accurate positioning.
The Lasers were mounted in wooden blocks that swivelled and could be adjusted by bolts from the sides.


CIRCUIT FUNCTIOन     

Speed Trap block diagram

Thanks to the PIC, most of the circuitry is interface control, such as buffers and drivers. The last 8 display digits are multiplexed, where only one digit is on at any one time, but all very quickly. To maintain brightness the LEDs are driven much harder than usual so protection was put in to detect if the clock ever stopped because of the PIC locking up for some random reason. In this way as soon as the display is frozen, the outputs from the shift registers is switched off. and thus in turn the display.

 

LED DISPLAY

he display is made up of 294 LEDs. These are divided up as follows: 

• A fixed 5 character display to show the word "Speed"
• Digits D to H are for the 5 digits displaying numbers and most of the alphabet letters (except for k,m,v,w,x).
• Digits C to A are for the display of the units, either "mph" or "mps" 
•  
•  

CIRCUIT DIAGRAM 

http://www.edutek.ltd.uk/Proj_SpeedTrap.html

SPEED TRAP

    

This was designed for a radio controlled car track using cars of 1/10 scale. It works by measuring the time it takes for an object to pass 2 sensors placed exactly 200mm apart. In this way the speed can be calculated in "MPH" and ms-1.

In fact 2 versions were made with the second designed exactly the same but the case was designed for indoor use.  

Designed and built by Phil Townshend 2008

DESCRIPTION

The principle is simple. Take the time it takes to travel 200mm, multiply this by 5 to get the time for 1 metre then take the reciprocal.
eg: Time taken to pass 200mm = 0.1s. Then 1 metre takes 5 x 0.1 = 0.5s,
so speed = 1 / 0.5 = 2 m/s.
The speed is displayed in metres/second by default, but pressing SW2 will display the speed in MPH but at a scale speed so actually it will read 10x as much. 
The Math routines I wrote I am very pleased with. They can multiply 16bit by 8 bit numbers and are based on long division and multiplication. I wrote them myself - honest!!

The sensors used were opto-transistors and the light sources were some 1mW keyring laser pointers (I found a deal on 30 for £10 from Japan - free shipping - bargain!) The lasers and sensors were positioned such that a beams were directed across the track exactly 200mm apart. The cars would break the beams as they drove past.

Boxes were made up from 6mm MDF to protect the sensors and Laser modules and also to ensure accurate positioning.
The Lasers were mounted in wooden blocks that swivelled and could be adjusted by bolts from the sides.


CIRCUIT FUNCTIOन     

Speed Trap block diagram

Thanks to the PIC, most of the circuitry is interface control, such as buffers and drivers. The last 8 display digits are multiplexed, where only one digit is on at any one time, but all very quickly. To maintain brightness the LEDs are driven much harder than usual so protection was put in to detect if the clock ever stopped because of the PIC locking up for some random reason. In this way as soon as the display is frozen, the outputs from the shift registers is switched off. and thus in turn the display.

 

LED DISPLAY

he display is made up of 294 LEDs. These are divided up as follows: 

• A fixed 5 character display to show the word "Speed"
• Digits D to H are for the 5 digits displaying numbers and most of the alphabet letters (except for k,m,v,w,x).
• Digits C to A are for the display of the units, either "mph" or "mps" 
•  
•  

CIRCUIT DIAGRAM 

http://www.edutek.ltd.uk/Proj_SpeedTrap.html

located at http://www.example.com/sitemap.xml, it can't include URLs from http://subdomain.example.com.
URLs that are not considered valid are dropped from further consideration. It is strongly recommended that you place your Sitemap at the root directory of your web server. For example, if your web server is at example.com, then your Sitemap index file would be at http://example.com/sitemap.xml. In certain cases, you may need to produce different Sitemaps for different paths (e.g., if security permissions in your organization compartmentalize write access to different directories).
If you submit a Sitemap using a path with a port number, you must include that port number as part of the path in each URL listed in the Sitemap file. For instance, if your Sitemap is located at http://www.example.com:100/sitemap.xml, then each URL listed in the Sitemap must begin with http://www.example.com:100.

Sitemaps & Cross Submits

To submit Sitemaps for multiple hosts from a single host, you need to "prove" ownership of the host(s) for which URLs are being submitted in a Sitemap. Here's an example. Let's say that you want to submit Sitemaps for 3 hosts:

www.host1.com with Sitemap file sitemap-host1.xml

www.host2.com with Sitemap file sitemap-host2.xml

www.host3.com with Sitemap file sitemap-host3.xml

Moreover, you want to place all three Sitemaps on a single host: www.sitemaphost.com. So the Sitemap URLs will be:

http://www.sitemaphost.com/sitemap-host1.xml

http://www.sitemaphost.com/sitemap-host2.xml

http://www.sitemaphost.com/sitemap-host3.xml

By default, this will result in a "cross submission" error since you are trying to submit URLs for www.host1.com through a Sitemap that is hosted on www.sitemaphost.com (and same for the other two hosts). One way to avoid the error is to prove that you own (i.e. have the authority to modify files) www.host1.com. You can do this by modifying the robots.txt file on www.host1.com to point to the Sitemap on www.sitemaphost.com.
In this example, the robots.txt file at http://www.host1.com/robots.txt would contain the line "Sitemap: http://www.sitemaphost.com/sitemap-host1.xml". By modifying the robots.txt file on www.host1.com and having it point to the Sitemap on www.sitemaphost.com, you have implicitly proven that you own www.host1.com. In other words, whoever controls the robots.txt file on www.host1.com trusts the Sitemap at http://www.sitemaphost.com/sitemap-host1.xml to contain URLs for www.host1.com. The same process can be repeated for the other two hosts.
Now you can submit the Sitemaps on www.sitemaphost.com.
When a particular host's robots.txt, say http://www.host1.com/robots.txt, points to a Sitemap or a Sitemap index on another host; it is expected that for each of the target Sitemaps, such as http://www.sitemaphost.com/sitemap-host1.xml, all the URLs belong to the host pointing to it. This is because, as noted earlier, a Sitemap is expected to have URLs from a single host only.

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Validating your Sitemap

The following XML schemas define the elements and attributes that can appear in your Sitemap file. You can download this schema from the links below:
For Sitemaps: http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd
For Sitemap index files: http://www.sitemaps.org/schemas/sitemap/0.9/siteindex.xsd
There are a number of tools available to help you validate the structure of your Sitemap based on this schema. You can find a list of XML-related tools at each of the following locations:

http://www.w3.org/XML/Schema#Tools
http://www.xml.com/pub/a/2000/12/13/schematools.html
In order to validate your Sitemap or Sitemap index file against a schema, the XML file will need additional headers as shown below.
Sitemap:

<?xml version='1.0' encoding='UTF-8'?>

<urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd"

         xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">

   <url>

      ...

   </url>

</urlset>

Sitemap index file:

<?xml version='1.0' encoding='UTF-8'?>

<sitemapindex xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/siteindex.xsd"

         xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">

   <sitemap>

      ...

   </sitemap>

</sitemapindex>

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Extending the Sitemaps protocol

You can extend the Sitemaps protocol using your own namespace. Simply specify this namespace in the root element. For example:

<?xml version='1.0' encoding='UTF-8'?>

<urlset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

         xsi:schemaLocation="http://www.sitemaps.org/schemas/sitemap/0.9 http://www.sitemaps.org/schemas/sitemap/0.9/sitemap.xsd"

         xmlns="http://www.sitemaps.org/schemas/sitemap/0.9"

         xmlns:example="http://www.example.com/schemas/example_schema"> <!-- namespace extension -->

   <url>

      <example:example_tag>

         ...

      </example:example_tag>

      ...

   </url>

</urlset>

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Informing search engine crawlers

Once you have created the Sitemap file and placed it on your webserver, you need to inform the search engines that support this protocol of its location. You can do this by:

• submitting it to them via the search engine's submission interface
• specifying the location in your site's robots.txt file
• sending an HTTP request

The search engines can then retrieve your Sitemap and make the URLs available to their crawlers.

Submitting your Sitemap via the search engine's submission interface

To submit your Sitemap directly to a search engine, which will enable you to receive status information and any processing errors, refer to each search engine's documentation.

Specifying the Sitemap location in your robots.txt file

You can specify the location of the Sitemap using a robots.txt file. To do this, simply add the following line including the full URL to the sitemap:

Sitemap: http://www.example.com/sitemap.xml

This directive is independent of the user-agent line, so it doesn't matter where you place it in your file. If you have a Sitemap index file, you can include the location of just that file. You don't need to list each individual Sitemap listed in the index file.
You can specify more than one Sitemap file per robots.txt file.

Sitemap: http://www.example.com/sitemap-host1.xml

Sitemap: http://www.example.com/sitemap-host2.xml

Submitting your Sitemap via an HTTP request

To submit your Sitemap using an HTTP request (replace <searchengine_URL> with the URL provided by the search engine), issue your request to the following URL:

<searchengine_URL>/ping?sitemap=sitemap_url

For example, if your Sitemap is located at http://www.example.com/sitemap.gz, your URL will become:

<searchengine_URL>/ping?sitemap=http://www.example.com/sitemap.gz

URL encode everything after the /ping?sitemap=:

<searchengine_URL>/ping?sitemap=http%3A%2F%2Fwww.yoursite.com%2Fsitemap.gz

You can issue the HTTP request using wget, curl, or another mechanism of your choosing. A successful request will return an HTTP 200 response code; if you receive a different response, you should resubmit your request. The HTTP 200 response code only indicates that the search engine has received your Sitemap, not that the Sitemap itself or the URLs contained in it were valid. An easy way to do this is to set up an automated job to generate and submit Sitemaps on a regular basis.
Note: If you are providing a Sitemap index file, you only need to issue one HTTP request that includes the location of the Sitemap index file; you do not need to issue individual requests for each Sitemap listed in the index.

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Excluding content

The Sitemaps protocol enables you to let search engines know what content you would like indexed. To tell search engines the content you don't want indexed, use a robots.txt file or robots meta tag. See robotstxt.org for more information on how to exclude content from search engines.

Romote Control Switch

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.





RC (Remote Control) Switch




It is sometimes necessary for an RC (remote control) model to contain some kind of switching functionality. Some things that come to mind are lights on a model boat, or the folding away of the undercarriage of an aeroplane, etc. A standard solution employs a servo, which then actually operates the switch. Separate modules are also available, which may or may not contain a relay. A device with such functionality is eminently suitable for building yourself. The schematic shows that it can be easily realised with a few standard components.

Picture of the project:

RC Switch Circuit

The servo signal, which consists of pulses from 1 to 2 ms duration, depending on the desired position, enters the circuit via pin 1 of connector K1. Two buffers from IC2 provide the necessary buffering after which the signal is differentiated by C2. This has the effect that at each rising edge a negative start signal is presented to pin 2 of IC1. D1 and R4 make sure that at the falling edge the voltage at pin 2 of IC2 does not become too high. IC1 (TLC555) is an old faithful in a CMOS version. A standard version (such as the NE555) works just as well, but this IC draws an unnecessarily high current, while we strive to keep the current consumption as low as possible in the model. The aforementioned 555 is configured as a one-shot. The pulse-duration depends on the combination of R2/C1. Lowering the voltage on pin 5 also affects the time. This results in reducing the length of the pulse. In this circuit the pulse at the output of IC will last just over 1.5 ms when T1 does not conduct.

Circuit diagram:

RC Switch Circuit Diagram

When T1 does conduct, the duration will be a little shorter than 1.5 ms. We will explain the purpose of this a little later on. Via IC2.C, the fixed-length pulse is, presented to the clock input of a D-flip-flop. As a consequence, the flip-flip will remember the state of the input (servo signal). The result is that when the servo-pulse is longer than the pulse form the 555, output Q will be high, otherwise the output will be low. It is possible, in practice, that the servo signal is nearly the same length as the output from the 555. A small amount of variation in the servo signal could therefore easily cause the output to ‘chatter’, that is, the output could be high at one time and low the next. To prevent this chatter there is feedback in the form of R1, R3 and T1. This circuit makes sure that when the flip-flip has decided that the servo-pulse is longer than the 555’s pulse (and signals this by making output Q high), the pulse duration from the 555 is made a little shorter. The length of the servo-signal will now have to be reduced by a reasonable amount before the servo-pulse becomes shorter than the 555’s pulse.

Parts and PCB layout

:

Parts and PCB layout Of RC Switch

The moment this happens, T1 will stop conducting and the mono-stable time will become a little longer. The servo-pulse will now have to be longer by a reasonable amount before the flip-flip changes back again. This principle is called hysteresis. Jumper JP1 lets you choose between the normal or inverted output signals. Buffers IC2.D through to IC2.F together with R5 drive output transistor T2, which in turn drives the output. Note that the load may draw a maximum current of 100 mA. Diode D2 has been added so that inductive loads can be switched as well (for example, electrically operated pneu-matic valves).

COMPONENTS LIST:

Resistors: R1 = 470k

R2 = 150k

R3 = 47k

R4 = 100k

R5 = 4k7

Capacitors:

C1 = 10nF

C2 = 1nF

C3,C4 = 100nF

Semiconductors:

D1 = BAT85 or similar Schottky diode

D2 = 1N4148

IC1 = CMOS 555 (e.g., TLC555 or ICM7555)

IC2 = 4049

IC3 = 4013

T1,T2 = BC547B

Miscellaneous: JP1 = jumper with 3-way pinheader

K1 = servo cable

K2 = 2-way pinheader or 2 solder pins

SPEED TRAP

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.

SPEED TRAP

    

This was designed for a radio controlled car track using cars of 1/10 scale. It works by measuring the time it takes for an object to pass 2 sensors placed exactly 200mm apart. In this way the speed can be calculated in "MPH" and ms-1.

In fact 2 versions were made with the second designed exactly the same but the case was designed for indoor use.  

Designed and built by Phil Townshend 2008

DESCRIPTION

The principle is simple. Take the time it takes to travel 200mm, multiply this by 5 to get the time for 1 metre then take the reciprocal.
eg: Time taken to pass 200mm = 0.1s. Then 1 metre takes 5 x 0.1 = 0.5s,
so speed = 1 / 0.5 = 2 m/s.
The speed is displayed in metres/second by default, but pressing SW2 will display the speed in MPH but at a scale speed so actually it will read 10x as much.
The Math routines I wrote I am very pleased with. They can multiply 16bit by 8 bit numbers and are based on long division and multiplication. I wrote them myself - honest!!

The sensors used were opto-transistors and the light sources were some 1mW keyring laser pointers (I found a deal on 30 for £10 from Japan - free shipping - bargain!) The lasers and sensors were positioned such that a beams were directed across the track exactly 200mm apart. The cars would break the beams as they drove past.

Boxes were made up from 6mm MDF to protect the sensors and Laser modules and also to ensure accurate positioning.
The Lasers were mounted in wooden blocks that swivelled and could be adjusted by bolts from the sides.


CIRCUIT FUNCTIOन    

Speed Trap block diagram

Thanks to the PIC, most of the circuitry is interface control, such as buffers and drivers. The last 8 display digits are multiplexed, where only one digit is on at any one time, but all very quickly. To maintain brightness the LEDs are driven much harder than usual so protection was put in to detect if the clock ever stopped because of the PIC locking up for some random reason. In this way as soon as the display is frozen, the outputs from the shift registers is switched off. and thus in turn the display.

 

LED DISPLAY

he display is made up of 294 LEDs. These are divided up as follows:

• A fixed 5 character display to show the word "Speed"
• Digits D to H are for the 5 digits displaying numbers and most of the alphabet letters (except for k,m,v,w,x).
• Digits C to A are for the display of the units, either "mph" or "mps" 
•  
•  

CIRCUIT DIAGRAM 

http://www.edutek.ltd.uk/Proj_SpeedTrap.html

1.2 - 12V / 1A Low Voltage Power Supply Using LM317 LED Indicator

Free Electronic/electric Circuit diagram for many electronic project, electrical project and electromachanical.


 

Project Description

This is a 1.2 - 12 V, max 1A power supply with a low voltage indicator LED. The indicator part includes three diodes and one LED. For example you are charging a battery, you can observe the charge status at that moment. Another advantage of this circuit, when the drawn current exceeds 1A (practically 0.85A), the current protector in LM317 intervenes and LED indicator warns you about the very low output voltage.

Be careful while choosing the transformer. Most of the products are specified as 10VA but their outputs are not as said.

Another good property of this circuit is the mains noise does not pass to the DC part.

The Simplest Line Follower

The new robot uses very little wiring. None of the wires have been soldered. I have also replaced the mounts for the sensors. I will describe everything in today’s post.
Before we begin, you’ll need to know how to design and build your own PCBs. A friend of mine has written excellent, very well explained tutorials for this. He uses Eagle. I will try learning KiCad for you free software folks. I’m having trouble with it though (Do pop in a comment if you would like to help me out) . Here are the links to the tutorials:

1. Eagle Schematic and PCB tutorial
2. PCB etching tutorial

I would suggest going over his circuit if you need some confidence. I made the line follower circuit for my first PCB. It’s simple too so you could try that as your first PCB.
Assuming you know how to make PCBs, here’s what you do. Make one main PCB for the L293D. You’ll need two other small PCBs to put the sensors. I’ve uploaded the eagle files containing my designs. You can download these from the Box.net widget on the right sidebar. Look for bruno-eagle-files.zip and LEDLDR-eagle-files.zip. I would suggest designing the PCB yourself for practice. Your design may be much better. I have a lot of inconsistencies in mine.
Here are photos of my PCBs:
The main L293D PCB:


All that labelling was to make the soldering easier. However I messed up while using the lacquer spray. You’ll see the results of that shortly. Now here are the PCBs for the LED-LDR sensor:


So those are the boards. Also remember to drill holes for the main PCB. I forgot to do this till the end. Drilling after soldering is a pain. Next step is to solder the components. Check all connections with a multimeter. At this point you can even check if the LEDs are lighting up and if the LDR sensors are working. Remember – do not plug in the chip till you have done this bit of testing. After you’ve checked that all the voltages are right, put a protective coat over the copper side of the PCB. I used lacquer spray. Unfortunately I forgot it is acetone based and made a mess of the labelling of the L293D PCB. Here is how it all looks now:


As you can see, I should have left a little more space at the edges. The copper in the photo is tarnished. It took a while for me to buy lacquer so this happened by then. A bit of sandpaper got it all cleaned up. My suggestion is to put the protective coating soon after you’re done soldering. Note that I have used berg pins instead of soldering the wires directly. Here is how I soldered the sensors:


Now that the electronics is mostly done, lets move on to the chassis. I used the same mechano plate as last time. For the sensors, I also used a mechano part. Note a few differences in the photos you are going to see and the actual robot. The photos below shows the 4-hole part. I replaced this with a 5-hole one later. Also I moved the PCB up to the front as the wires weren’t long enough. Finally I had to change the wheels as this construction was very unstable. You’ll see the corrections in the last photo. For the connections, I used female jumper wires such as these:

Before fixing the PCBs to the base, make sure you put something to protect the copper side. We do have a coating but better be safe than sorry. I used pieces of cardboard.

The chassis:

The corrected version. The sensor mounts are folded. I’ll explain this next. Notice how I used some screws to sort out the motor’s wires. I’ve kept these wires long as I’ll be using the same motors for other robots as well.

See how neat this is compared to the original robot? Finally here are a few photos of the complete robot.

Observe how the sensors have been mounted here. Metal mounts = no bending, if you’re careful enough of course. I found a big advantage of using these plates only after I completed the robot. You can fold these sensors under the main base. This further protects them from damage when you store the robot. This is what I mean:

Pretty neat isn’t it? Finally these plates also make adjusting the distance between the sensors a lot easier. With the cardboard mount, you’d have to replace it each time the width of the line changed. In the new robot’s case it’s very simple:

As indicated above, you can freely adjust both the plate as well as the PCB. Again, remember to protect the copper side with something like cardboard. Finally, connect the batteries and you’re good to go:



I used larger wheels so the robot was a bit too fast. (v = r x ω). I put the batteries at the front to slow it down. It slows down because the friction on the front castor wheel increases. If you use the small wheels like last time, keeping the batteries at the back should work. Another reason to keep the batteries ahead is that it makes the robot more stable. Unfortunately the wires I used were too short so the PCB had to go to the front and the battery space got pushed back. I’ll probably join two wires to increase the length when I get time.
So that is the new and improved line follower! Hope you like this little upgrade.

For my next activity, I will do the same upgrade for the table follower. We shifted to a new place last year and both robots, especially the table follower, were damaged in the process. The table follower’s mounts are broken. These new metal plates should make a more robust bot. I will also try to make it smaller by making smaller PCBs. I wasted a lot of space in this PCB as it was my first time.
I have also bought a bit of equipment. I will blog about it either during the week or on the weekend so stay tuned for details of my lab in progress
Please do tell me what you think in the comments below. I’m sure you will have much better ideas and I’d love to hear you out. Thanks for reading!

Update 1

I was able get longer jumper wires and reverted to the smaller wheels. I also used smaller beams for the sensors. Here is how my robot looks now.


I also changed the motors to 150RPM. I’ll be using the 200RPM motors for the table follower update. I should hopefully be done this weekend.