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#25250
"Now only if we could get people to RTFM." :mrgreen:
That will never happen, but i see your frustration.
I think both you and David do a marvelous job, without being paid.
David must be extremely wealthy, Karma vise....... :D
Good job both of you.
Keep it up, Hasse.
#25304
Where is the post for this drawing.
Image

I can't find it in a search because I don't know what it's pertaining to, so I don't know what to type in for a search.

Someone on FB is having a problem and we can't workout the drawing exactly., ie it says pullup but it's pulling down to GND, and the reversed diode, unless it's a 5V Zener.
Last edited by Old Grey on Sat Jul 07, 2018 11:20 pm, edited 1 time in total.
#25306
Old Grey wrote:
Sun Apr 01, 2018 12:49 pm
Someone on FB is having a problem and we can't workout the drawing exactly., ie it says pullup but it's pulling float to GND, and the reversed diode, unless it's a 5V Zener.
+1 to Weaver's response. Perhaps outline the issue here or in it's own thread. The only time this would present a problem is if the input device (sensor, module, etc.) had an active high greater than 5V, such as +12V (expected, and purpose fo the circuit), but had only an inactive float without ever going to ground (device output +12V-to-float, never grounding). In that case a much 'stronger' pulldown must be used to pull the input lower against the 5V pullup when the device is not high. I would just suggest the Speeduino 5V pullup resistor be 10k and the pulldown in the circuit be 1k to 2.2k max (10-20% of pullup value). This would ensure the float state was pulled to a voltage low enough through the diode to be seen as a low by Speeduino. I don't know what he's using, so testing the final input voltage levels before connecting the Mega would be a good idea to be sure it's all together and working as-expected.

Crappy explanation: The two things to be careful with here are 1) the current can become quite large without a small 10k pullup (the 1K pullup on some boards will pull ~30mA from the weak regulator and 1/4W of heat constantly), and 2) the diode forward voltage means the pullup will not ever be pulled completely to ground. This is OK as Speedy only needs it to be lower than 1.2V for a low, but the pulldown must be a balance of small enough to pull diode Vf + divider voltage = <1.2V, yet large enough the active high will be enough to reach at least 3.3V high on the Speeduino side of the diode. :roll: If all that poor hairball explanation isn't making enough sense for him, and his device is only outputting +12V and float (no grounding), just tell him to try the 10k pullup/1K pulldown suggestion above. ;) Again, I don't know what he's using, so testing the input voltage levels before connecting the Mega would be a good idea to be sure it's all together and working properly.

David
#25310
PSIG wrote:
Sun Apr 01, 2018 4:20 pm
Old Grey wrote:
Sun Apr 01, 2018 12:49 pm
Someone on FB is having a problem and we can't workout the drawing exactly., ie it says pullup but it's pulling float to GND, and the reversed diode, unless it's a 5V Zener.
+1 to Weaver's response. Perhaps outline the issue here or in it's own thread. The only time this would present a problem is if the input device (sensor, module, etc.) had an active high greater than 5V, such as +12V (expected, and purpose fo the circuit), but had only an inactive float without ever going to ground (device output +12V-to-float, never grounding). In that case a much 'stronger' pulldown must be used to pull the input lower against the 5V pullup when the device is not high. I would just suggest the Speeduino 5V pullup resistor be 10k and the pulldown in the circuit be 1k to 2.2k max (10-20% of pullup value). This would ensure the float state was pulled to a voltage low enough through the diode to be seen as a low by Speeduino. I don't know what he's using, so testing the final input voltage levels before connecting the Mega would be a good idea to be sure it's all together and working as-expected.

Crappy explanation: The two things to be careful with here are 1) the current can become quite large without a small 10k pullup (the 1K pullup on some boards will pull ~30mA from the weak regulator and 1/4W of heat constantly), and 2) the diode forward voltage means the pullup will not ever be pulled completely to ground. This is OK as Speedy only needs it to be lower than 1.2V for a low, but the pulldown must be a balance of small enough to pull diode Vf + divider voltage = <1.2V, yet large enough the active high will be enough to reach at least 3.3V high on the Speeduino side of the diode. :roll: If all that poor hairball explanation isn't making enough sense for him, and his device is only outputting +12V and float (no grounding), just tell him to try the 10k pullup/1K pulldown suggestion above. ;) Again, I don't know what he's using, so testing the input voltage levels before connecting the Mega would be a good idea to be sure it's all together and working properly.

David
Thank you a ton for this! The sensor itself is actually an optical sensor from an Isuzu 4ZE1. I don't have all the fancy tools (that I probably should have) to measure these things 'properly', but I did supply it 12v from the battery, and I watched the output on a multimeter. That was showing me pulses of 12v, which is what lead me onto your diagram. When the pulse was 'off' though, it went to 0v, so I guess that means I don't have to worry about the resistor and jumper, because it's 0v, not floating?
Also I don't know if I have the option of changing resistors in the speeduino, as I've bought mine assembled, and it's not actually here yet!
#29306
don't know if this has already been suggested....

could this thread be moved to the "getting started" section of the forum?

as a beginner, I only just discovered this by chance..... I'd been trawling the "getting started" forum until now.....

or even a sticky link from within the 'getting started ' section to this thread?

great post by the way...
#29319
Just a note that the circuit posted will work with the majority of situations, but if you find hardship with that simple mod, you can always run a plug-in signal conditioner module to accept the +12V (or whatever) signal. A signal conditioner module that will process a high/float signal that never goes negative will work, such as the DSC. Some such as the LM1815 and MAX chips don't always like signals that don't go negative to 'reset' for the next signal. ;)

David
#29911
I reckon Old Greys post is great, hey he is contributing isn't that what its about, now that diagram he posted - that helps me out immensely I'm not a electronics engineer, never touched EFI stuff before - but that diagram just made is very clear and concise as to what needs to happen - well done old grey !
#29915
Psig - I can confirm that the JimStim does work as an engine simulator. All Sensors respond as does the RPM. The only Issue I have seen is that the RPM only responds up to 2000 RPM. That may be a function of how the JimStim puts out its Rpm Signal but it does work thru the VR board.
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