Speedometer - transparent first-surface reflector needed!

[mike mager]

cwagner,  [I don't know the full name.]

I didn't mean to leave you hanging on the HUD stuff;  the problem for my 
system is finding a reflector more convenient than an aircraft type (mounted 
midway between the pilot and the windscreen).

[question]
How do you plan to handle the reflector?

[question]
Do you have any MCU experience?

A digital or text instrument of most any sort is easily constructed using, 
for example, a Microchip 16C74 PIC (please, let's avoid a holy war - most 
any MCU will work!).

I used a 16C74 because of the analog inputs, and the extra IO ports; a 
smaller (than  forty pins) one would be fine for a simple system.

[question]
Do you have a VSS or speed sensor of any sort, or will you be adding one?

The sensor's signal is conditioned by an NS circuit, if it is  a 
variable-reluctance unit, or tap it out of the vehicle's ECU!  A Hall-effect 
or optical sensor may require no conditioning.

Now, the MCU just counts the pulses for a 'gate period' (then resets the 
count), and the count is arithmetic'd for scaling to MPH, KPH, or other.  
Leading-zero suppression is easy  in firmware, then just serial it out to an 
NS serial-input constant-current LED display-driver, and vary the intensity 
of up to thirty-five LEDs with one trim.  A standard 15$ '780 LCD text 
display is only a bit more complicated to connect, and can then 'say' 
anything.  Bitmapped LCD displays require a drive, just 'a bit' more work.  
If you want VFD, they either require a driver, or have it on board (I have 
both types on my bench).

[Please, I beg for mercy, I just bashed this message out in about five 
minutes, without opening a data-book, and it is imperfect, I'm sure!]

Lemme know what you need/want/like/hate.

Mike
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