Honda D/B series tachometer signal help

Charlienofun · Post by **Charlienofun** » Tue Feb 24, 2015 7:13 pm

Hey Folks,

I tapped my civics tachometer line from the back of the cluster. When I measure with my multimeter set to AC at the RCP header I can see voltage move from 2v-8v that seems to correspond with built in tach (I guess PWM averaged by my meter). I set my sample rate to 1Hz Timer Speed is Medium (I tried the other two options as well). My Pulse per Revolution is set to 2 as per honda tech forum.. but I don't see anything after I write the config and switch back to the dashboard view.

Is there a step I'm missing? Maybe a generic debug view that will show pulses / voltages being read?

Car is gonna be in Chumpcar race this weekend @ thunderhill would love to get RPM working

Post by **brentp** » Tue Feb 24, 2015 7:51 pm

Hi Charlie,

Thanks for the post. I take it the RPM value is simply remaining at zero? Can you confirm what RPM port you are connecting the wire to? Note the first timer input is the outermost connection on the terminal block? You can also try the other inputs as well.

As far as the signal goes; we're not familiar with that connection on the honda. It would be best if a scope could be put on the line to make sure it's a relatively clean square wave signal; unfortunately a multi-meter doesn't tell enough.

This is a good writeup on the CoilX module so you can learn what it's like to clean up a noisy tach signal coming from the ignition coil primary: http://autosportlabs.net/CoilX

Not saying the line you tapped into is this kind of signal, but it's good background info.

Charlienofun · Post by **Charlienofun** » Tue Feb 24, 2015 9:09 pm

brentp wrote:Hi Charlie,

Thanks for the post. I take it the RPM value is simply remaining at zero? Can you confirm what RPM port you are connecting the wire to? Note the first timer input is the outermost connection on the terminal block? You can also try the other inputs as well.

As far as the signal goes; we're not familiar with that connection on the honda. It would be best if a scope could be put on the line to make sure it's a relatively clean square wave signal; unfortunately a multi-meter doesn't tell enough.

This is a good writeup on the CoilX module so you can learn what it's like to clean up a noisy tach signal coming from the ignition coil primary: http://autosportlabs.net/CoilX

Not saying the line you tapped into is this kind of signal, but it's good background info.

Hey Brent!

Thats correct I setup the main gauge in the first layout to show RPM and it just sits at zero. I also checked the other screens they are all showing the same. I am using the first input on the rail but I can try the 2nd one when I get home.

Will read up on coil x again.

Just to clarify there is no debug view for seeing what the device is reading on each port? I don't have an oscilloscope but I might be able to get access to one after the next race. If I can get it working I can post a tutorial for other Honda owners. I could see nasa Honda challenge racers being interested and just about all civics from the 90's use the same signal if I'm not mistaken.

Thanks,

Charlie

Post by **brentp** » Tue Feb 24, 2015 10:01 pm

There isn't any 'debugging' output in the firmware per se due to the embedded nature. for seeing the output all you need to check is the raw channels dashboard screen (green text indicators)

Knowing what that signal looks like would be important to know and seeing a 'scope trace of the signal would be helpful.

-Brent

Charlienofun · Post by **Charlienofun** » Tue Feb 24, 2015 10:43 pm

brentp wrote:There isn't any 'debugging' output in the firmware per se due to the embedded nature. for seeing the output all you need to check is the raw channels dashboard screen (green text indicators)

Knowing what that signal looks like would be important to know and seeing a 'scope trace of the signal would be helpful.

-Brent

A friend that has a portable scope and is bringing it over tonight. Does the raw channels screen show all values even if they are not currently reading anything? I only quickly skimmed that one but don't recall seeing any that weren't showing data but I wasn't paying much attention really just scanning for the RPM.

Thanks!

Post by **brentp** » Tue Feb 24, 2015 10:51 pm

The raw channels view will show all enabled channels in the configuration. Enabled means: The sample rate for a channel set to something other than "Disabled"

For example: If you enable Pulse Input 1 at 10Hz with no wire connected, it will show the channel in the raw dashboard view, with just no data (zero value).

When you test the signal with the scope, test the signal before connecting to RCP and then afterwards, probing right at the terminal block input.

Thanks!

Charlienofun · Post by **Charlienofun** » Wed Feb 25, 2015 6:05 am

So it is enabled and shows RPM 0.

At one point I thought it was working because the gauge was moving as I reved the motor but it was way off. I tried adjusting polling frequency and the other parameters but I think it was a fluke because now it either shows 0 or just stuck on 200 rpm then 13k

Didn't get to use scope really only had a little time for this in between finishing running gear related stuff on car. Might get more time tomorrow evening.

Charlienofun · Post by **Charlienofun** » Wed Feb 25, 2015 5:21 pm

Found this post showing a trace of the tach signal on a car with the same engine/ignition. Will still take my own but thought this might help if anyone else is trying to figure this out.

http://electronics.stackexchange.com/qu ... understand

Post by **brentp** » Wed Feb 25, 2015 5:24 pm

that looks like classic ignition coil flyback. the trace is similar to the writeup on our CoilX page.

Keep us posted!

PopKorn78 · Post by **PopKorn78** » Tue Mar 24, 2015 7:17 pm

Were you able to get a signal? I have the same issue with same car, RPM stays to 0.

Post by **brentp** » Tue Mar 24, 2015 7:20 pm

Can you get an 'scope trace of the signal coming out of the ECU? That would be very helpful for us to help you get RPM working.

If you don't have access to a scope, you can get a decent little unit on amazon for not much. Really valuable for probing signals around the car: http://www.amazon.com/SainSmart-Digital ... s=dso+nano

stingg · Post by **stingg** » Thu Jun 25, 2015 3:07 am

I managed to get the rpm signal from Honda B series without any other external electronics. Tap the signal from ICM wire I believe its A21 on OBD1 socket. Settings would be 4 signal per rev.

Post by **brentp** » Fri Jul 17, 2015 5:44 pm

Thanks! added the Honda info here in the wiki: http://autosportlabs.net/RaceCapturePro2_RPM#Honda