Digital Speedometer 12v

D

Deoodles

Well-Known Member
Wired this 6 ways from Sunday and no the odometer did not change to miles. I sent the vendor a picture with the mph and km circled. Asked him how to fix this. Hope he has one but I doubt it. Wire colors are not what he said they would be in his notes. No surprise. I wonder if the circuit could slow it down enough for kph to be mph.:whistle:
 
Adam-NLV

Adam-NLV

Well-Known Member
Oh, oK I know how that goes. I picked up one for 30 shipped. . Its strange to have mph & SI units too. Seems there would be a way to change it,
I'll Put it on the scope, when it arrives, see what we got coming out the sensor, when hooked to my power drill. :sneaky:
 
6

69ST

Well-Known Member
Deoodles said:
Wired this 6 ways from Sunday and no the odometer did not change to miles. I sent the vendor a picture with the mph and km circled. Asked him how to fix this. Hope he has one but I doubt it. Wire colors are not what he said they would be in his notes. No surprise. I wonder if the circuit could slow it down enough for kph to be mph.:whistle:
Click to expand...

Only way to find out is...the hard way. Get the unit dialed-in for speed accuracy, having someone in another vehicle pace you. Once that's been done, go a for ride over a known route...the longer the better. From my experience, "longer" is limited to about 10 miles. Beyond that, over the road, there are too many traffic variables.
 
D

Deoodles

Well-Known Member
Funny you bring that up. I have my 10 mile route verified. Just waiting for the circuit to arrive. I hope the project gets that far though. It could fail on the bench. The vendor I used is actually a nice guy. He emailed me last night and said he would ask the mfr about it. That’s way more than I expected from them.
 
Adam-NLV

Adam-NLV

Well-Known Member
Hey Ray, i got my digital speedometer!:)

I have it apart and want too look at the output of that sensor, which is the white socket I shown pulled.
Also found the formula so we can find the value of the capacitor and resistors that we need for our 555 timer circuit. Its in the pic its the yellow highlights resistor A & B and only one capacitor, C1. lol;)

Now we need to find the frequency coming out the sensor. I powered up my tektronik O'scope and its working, survived the move! (y)

As usual the speedometer has no wiring diagram, I dont want to email the vendor;so how is yours wired to power, is it
Black/green for ground and the Orange wire or the Red/grn for power?

Meanwhile I'll find a +12v source to use for power on the bench but by tomorrow I want to have it powered up and bench checked. I'll rotate the speedO cable with the drill and we can finally see the frequency coming out.

100_0202.JPG
 
Last edited:
D

Deoodles

Well-Known Member
image.jpg
This is what I got from the vendor. It didn’t exactly match but was close enough to get it wired. I used a molex connection to make it a clean installation
 
D

Deoodles

Well-Known Member
image.jpg For my Speedometer solid orange and solid light blue are for signals, red and green is ground, blue and black is positive and solid brown is positive for the display backlight. I also have the blue and green connected to the black and green to switch from KM to mph those came with connectors already attached And just needed to be plugged together. The green and yellow is for fuel I’m not using it
 
Last edited:
Adam-NLV

Adam-NLV

Well-Known Member
I took the harnss apart, they spliced grn/blk to solid green. So thats gotta be ground.

Now for power, I have a Black wire with blue stripe. I guess that's the 12v line? Is your black with a blue stripe?
 
Adam-NLV

Adam-NLV

Well-Known Member
Ok, got it powered up!
Mine is green is ground and Brown is power. lol Will hook it to the scope, powered with the drill check out the sensor frequency.
100_0207.JPG
 
Adam-NLV

Adam-NLV

Well-Known Member
Here's that signal pulse. , I got the frequency and its pretty slow, its 20ms.

So now we have the frequency. We'll use our 555 circuit to delay that 20ms signal around 5 ms and see if it calibrates the speed accurately.;)

I haven't got my 555 kit yet, i know yours came, maybe it will arrive today and we can build our timer, it will be pretty close to the one on youTube except we will use a potentiometer to calibrate the resistance for our circuit.
100_0013 (1).JPG
 
Last edited:
D

Deoodles

Well-Known Member
I can’t think this through is it better to slow down the KM mode or the mile per hour mode. Will one correct the odometer even though it says KM it’s still miles?
 
Adam-NLV

Adam-NLV

Well-Known Member
No problem, we can build it together online and it should be pretty straight forward.. Don't freak out if your circuit doesn't work the first time, cause they never do! lol:LOL:

Oh but the 555 is fool proof and a tough little chip, I think its perfect for a newbie circuit.:whistle:
 
D

Deoodles

Well-Known Member
Today I successfully made the 555 circuit. It took a while but I started at zero and Adam answered all questions along the way. I know this project is moving slowly but it’s moving. I am glad it’s progressing.
 
Adam-NLV

Adam-NLV

Well-Known Member
Hey, allright Ray! I knew you could get that 555 cranked up! That's a huge step congrats!;)


My TI (Texas instruments) 555 should be here by Monday, sorry for the delay, but we're getting there!(y)
 
Top