Digital Vehicle Speedometer Display

[indecided]

eight way switch and diodes to create binary data? Now i'm confused..

Think pull-up resistors on the four lines, with each switch connection taking different lines to ground via diodes - so for all ones you have no diodes, and the resistors pull all the lines HIGH. For all zeros you have diodes from each line, pulling them all LOW - for values inbetween you simply wire diodes accordingly.

how does eight individual pushbutton switches and a maze of diodes sound like?

In sounds like the switches don't latch 8)

Oh dear. I can't make much sense outta this.. I can roughly quantify the idea but have no inkling of a circut. Please do elaborate.. I'm pretty keen on using pushbutton switches instead of a rotary dial.

OTOH, am I supposed to be looking for a decimal/hexadecimal rotary?

parts num 333-091/333-085 on RS (Rotary Switches)

K, after spending a couple of days looking at info on rotary switches, I still can't deduce how to build individual pushbutton switches to create binary data out of resistors and diodes. gah... someone please help. :shock:

 

[Nigel Goodwin]

K, after spending a couple of days looking at info on rotary switches, I still can't deduce how to build individual pushbutton switches to create binary data out of resistors and diodes. gah... someone please help. :shock:

I never suggested pushbutton switches! - you would need considerable electronics to make them latch. What I was suggesting was a single pole eight way rotary switch, along with a handful of diodes to produce a binary sequence.

 

[indecided]

Ah. That being the case, I just ordered a Thomas & Belts BCD rotary switch.. i'm supposed to get the decimial one and NOT the hexa right? Guess i could afford it since Microchip has been kind enough to sponsor a trio of 16F628As for me

 

[indecided]

anyways, I also wanted to ask :

is this programmer (F-84 specific) 100% compatible with the F628A?

I know the 628 is backwards compatible but just want to be sure before I build it

**broken link removed**

 

[Nigel Goodwin]

anyways, I also wanted to ask :

is this programmer (F-84 specific) 100% compatible with the F628A?

I know the 628 is backwards compatible but just want to be sure before I build it

**broken link removed**

As it's specified as compatible with my software it should work fine for the 16F628A.

 

[mataston]

hi i have had lots of fun reading this article i also wish to do the same thing build a digital speedo, i have the facility for programming pics, there is a counter i.c which will run an lcd unit direct available from maplin. all i want the pic to do is count the pulses coming in then when it reaches a set figure it then sends out a clock pulse. 300 revolutions of the proshaft = 1 mile. so after the pic has reached a count of 300 pulses from a hall effect device it sends out 1 clk pulse to the counter. but i need it obviously to retain the information after power off can any one help on this?????

 

[fever]

may be i shld have search first.but i was looking for it in micro controllers division.
any way have a look
https://www.electro-tech-online.com/threads/digital-speedometer-using-at90s2313.21650/
as i dono much abt microcontroller i want u ppl to have a look
an avr coupled with halleffect looks good to me.

 

[nandishsmantur]

the approiate circuit diagram of digital speedometer based on pic microcontroller based laser sensing of rotation of wheel.

 

[steev]

i think this is what u want
http://www.sprut.de/electronic/pic/projekte/dehzahl/dreh.htm
eng version: **broken link removed**

 

[Neil.r]

Yes, just a standard LCD module, they used a 2x8 one in the original article.



The other two chips are on a seperate board, and not relevent to your design - they are a PLL and a schmitt trigger - they were used to provide a pulse output from the FGM-3 sensor used in the design.

The circuits for the project are only in one part, there is a second part, which deals with setting it up etc.



It's got connections for ICSP using the EPE TK series of programmers.



There are seven different modes:

Mode 0) Trip elapsed time and distance (km).
Mode 1) Current speed and average speed (km/h).
Mode 2) Peak speed and total difference (km/h).
Mode 3) Trip elapsed time and distance (miles).
Mode 4) Current speed and average speed (miles/h).
Mode 5) Peak speed and total difference (miles/h).
Mode 6) Current wheel rotation count, and average over ten seconds.
Mode 7) Visual warning of reset contdown on both lines.


WD1 is an audio buzzer, for audible indications. Sk1 is simply the external conenction to the board - basically power positive and negative, and a pulse input.



You would need to rewrite the entire display routines, probably using interrupts to multiplex the displays - see my tutorials for an example.



If I get time I'll scan the whole article.

Hi Nigel
Could you send me a copy of the scanned project, I can not find a copy of it on EPE's web site, I guess it it too old!
I wish to make a speedo for a 5 inch model loco, (wheel size around 3.5 inch to 5 inch) maybe also 7 1/4 inch loco (5 to 7 inch wheel) and I think this may help me, I was planning to use the later PIC 16F628, an 2 x 16 LCD,

Neil