Need help on digital speedometer

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Need help on digital speedometer

Postby Fiz » Wed Nov 09, 2011 12:13 am

Greetings,recently i was given a task to make a mini project, mean simple circuit with plain application. So i decided to make a digital speedometer for motorcycle and i choose making a mechanical digital speedometer. The problem i facing here is, finding the right circuit for the project since there are cluster of circuit on internet and complex circuit all over the books.. totally newbie and inexperienced in electronic :(
Even i couldn't pick the suitable circuit, i still got opinions and here i attached the circuit get my attention:-
The attachment speedo.png is no longer available


And this is the website http://martybugs.net/electronics/speedo.cgi

Do not hesitate to give any thought and suggestions,i totally will appreciate it!! So, please leave comment
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Re: Need help on digital speedometer

Postby shahrul » Wed Nov 09, 2011 9:06 am

Why not, you try construct that circuit first. Then you will know the functionality. Then the circuit can be reduced using microcontroller.
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Re: Need help on digital speedometer

Postby Fiz » Wed Nov 09, 2011 10:46 am

Thanks for your response.I actually want to ask, should i construct on breadboard or just with multisim,isis,etc..because i'm clueless..and i didnt want to involving pic or micro p..could i?
Please give me more suggestion.. :roll:
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Re: Need help on digital speedometer

Postby shahrul » Wed Nov 09, 2011 11:09 am

Fiz WROTE:Thanks for your response.I actually want to ask, should i construct on breadboard or just with multisim,isis,etc..because i'm clueless..and i didnt want to involving pic or micro p..could i?
Please give me more suggestion.. :roll:

For me, I like to construct on stripboard. I don't like breadboard because it's will involve many jumper and the jumper connection also sometimes loose. If troubleshoot, many error possibility.

I'm not doing simulation also because the simulation is not exactly same as actual. Sometimes doing simulation success, but actual not running.
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Re: Need help on digital speedometer

Postby Fiz » Wed Nov 09, 2011 11:53 am

shahrul WROTE::
For me, I like to construct on stripboard. I don't like breadboard because it's will involve many jumper and the jumper connection also sometimes loose. If troubleshoot, many error possibility.


Great idea,btw, stripboard is copper board with holes(perfboard) right? And actually i'm short of modal so i have to specific the items that i really need and i wish some1 could explain abit about the circuit bcause its messed me up..
Thanks for replying..and really look forward from you..~~
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Re: Need help on digital speedometer

Postby ABSF » Tue Nov 15, 2011 9:42 pm

Fiz WROTE:Greetings,recently i was given a task to make a mini project, mean simple circuit with plain application. So i decided to make a digital speedometer for motorcycle and i choose making a mechanical digital speedometer. The problem i facing here is, finding the right circuit for the project since there are cluster of circuit on internet and complex circuit all over the books.. totally newbie and inexperienced in electronic :(
Even i couldn't pick the suitable circuit, i still got opinions and here i attached the circuit get my attention:-

Do not hesitate to give any thought and suggestions,i totally will appreciate it!! So, please leave comment


I've been to the site you pointed and roughly glance thru the circuit. The display part is straight forward and it is quite similar to a kits sold by ESCOL.

http://www.escol.com.my/kits/ES-012.html

I did a similar project for my bicycle but used a PIC16F628. The principle is almost the same but I only put one magnet on the front wheel spoke. The detector is a reed switch instead of induction coil. It was calibrated using a 555 oscillator.

The front end of your circuit is a bit difficult for me to understand. From calculation the IC2 555 will generate square pulses of 7-19 Hz. At the speed of 42.16 Km/h which is equivalent to sending 50 pulses per second to the circuit. Since there are 2 magnets mounted on the wheel which means that there are 2 pulses per revolutions of the wheel, the formula uses 25Hz (50Hz/2) for calculation to obtain the speed of 42.16 Km/h. The 555 output is divided into 10 parts by the 4017 where the time period of 8 parts allows the pulses from the detector (inductor) to be counted and accumulated in the 4553. On the 9th period, the counters are latched into the 4511 decoder and displayed. On the 10th pulse, the 4553 is reset and starts counting from the wheel again.

Once the 555 is calibrated and remains at that freq., and the speed is increased (let's say by 2) to 84.32 Km/h, there should be 100 pulses/S entering the circuit which makes the display to show 84 Km/h.

In the formula, there is a constant called diff ratio and I cannot understand what it's for and that's what puzzles me.

Allen
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Re: Need help on digital speedometer

Postby Fiz » Tue Nov 15, 2011 10:39 pm

HELoooooo Allen~~~~As always and expected, u sooo awesome!! Thanks for replying and your enlightenment also the information..Its so nice to know your opinion, uhmm..what actually i'm trying to do here is, a sensor(to detect the speed,btw idk what term of method to get the speed maybe rpm or other easier method) attached to the bicycle spinning part;shaft? or at the brake gripper(by remove the gripper(rubber) and replace with the sensor and interface with I.C to interpret it(frequency to voltage I.c probably; LM2917? or... i hunger your opinion actually..) and connect to the display(7 segment;maybe used up to 2 or 3 segments). But,i prefer to take toy cars as the modal instead of bicycle..Anyways, you are my savior..for real~~Thanks again.
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Re: Need help on digital speedometer

Postby ABSF » Wed Nov 16, 2011 11:10 pm

Fiz WROTE:HELoooooo Allen~~~~As always and expected, u sooo awesome!! Thanks for replying and your enlightenment also the information..Its so nice to know your opinion, uhmm..what actually i'm trying to do here is, a sensor(to detect the speed,btw idk what term of method to get the speed maybe rpm or other easier method) attached to the bicycle spinning part;shaft? or at the brake gripper(by remove the gripper(rubber) and replace with the sensor and interface with I.C to interpret it(frequency to voltage I.c probably; LM2917? or... i hunger your opinion actually..) and connect to the display(7 segment;maybe used up to 2 or 3 segments). But,i prefer to take toy cars as the modal instead of bicycle..Anyways, you are my savior..for real~~Thanks again.


Thank you for your kind compliments but I know I am not that good as you thought :oops:

My bike computer is based on the article here:

http://www.piclist.com/techref/piclist/ ... /index.htm

On chapter 10, the author mentioned about the sensor using hall effect detector which is different from mine. In order to mount the sensor, you can refer to the diagram here:
http://www.ebay.com.my/itm/LCD-Bicycle- ... 27bbe19306

Scroll further down and you will find the diagram how to mount the magnetic sensor on the front wheel.
As for the use of LM2917, few years ago, my friend has designed a RPM meter based on this chip but the result was not so good. In his design, he used an anlogue meter to measure the voltage converted from frequency. The RPM that he measured was very low, like 100 to 600 RPM. When the RPM is low it took long time to update the meter. Later his switched his design using PIC and that worked successfully. He now has a version using 16F877A and was able to measure RPM on both right and left engines. It even took care of the reverse direction by displaying the word "ASTERN" underneath the rpm number in the LCD display. He told me the program was written in PIC Basic Pro.

cheers ;)

Allen
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Re: Need help on digital speedometer

Postby Fiz » Tue Nov 22, 2011 1:03 am

Helo again and thanks for the commitment, i'm very sorry for my disabilities to complete my mini project with your reference but there still a lot of ideas come from your brilliant suggestions, as i mention at earlier, i could not use pic and micro c/p due to some reason, i got something to show to you,take a look
http://www.instructables.com/id/Tamiya- ... ed-sensor/

Very similar with what i want to make,just i need to build tachometer and the display.

Regards,Fiz
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Re: Need help on digital speedometer

Postby ABSF » Tue Nov 22, 2011 9:56 am

Fiz WROTE:Helo again and thanks for the commitment, i'm very sorry for my disabilities to complete my mini project with your reference but there still a lot of ideas come from your brilliant suggestions, as i mention at earlier, i could not use pic and micro c/p due to some reason, i got something to show to you,take a look
http://www.instructables.com/id/Tamiya- ... ed-sensor/

Very similar with what i want to make,just i need to build tachometer and the display.

Regards,Fiz


A tachometer is different from a speedometer or odometer. The tachometer measures RPM (Revolutions per minute) while the speedo measures KM/H (KM per hour) or MPH (miles per hour). Of course you can calculate the KM/H from the RPM with some known constants like the circumference of your wheel and the relationship between the rpm and the revolution of the wheel. From your web site I think what you need is a speedometer or odometer.

Just stick to your original circuit and you should be able to make it work. Just use the diff ratio of 3.9 and measure the wheel perimeter of your sports car in cm. and substitute them into the formulae. use 50Hz instead of 25Hz for the formulae and you can reduce the magnet to only one which gives one pulse per revolution and it will be easier for you to construct.

Without using a PIC or any microcon, the circuit would tend to be quite complicated. and I cannot think of any way to simplify the circuit. I found one schematic using just 2 chips but it was used for measuring the rpm and not kmh. The output is in analogue form and not digital.

http://www.edaboard.com/thread170692.html

If you just want to have a rough idea of how fast your car is moving, then it should be easy for you as you have already used the LM3914 before. :P

Allen
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