I'm hoping someone can take a moment to help me and possible restor my sanity!
I'm stuck with a 14-pin LM2917 - i've got an 8-pin on order now, but damn it, I want to get this to work.
I've built this on a breadboard using a modified version of GitHub - designer2k2/multidisplay: The MultiDisplay Project, An opensource datalogger, boost controller and display for cars . I have then used the datasheet as well as this schematic to convert to 14 pin... :
So heres what I ended up with - its ugly as a schematic because I've re-worked it to match the orientation/layout of the breadboard to help debug...
And heres my breadboard layout:
Hi-Res Version! <-- that should allow you to see all the components hooked up ok... I hope...
Yellow is frequency in, White is the LM's RC circuit, Blue is Signal Out. To help save hands, I hooked an LED up to the output signal.
Now... I'm not game to hook it to my 'duino nor can I be buggered going out to the bike yet... so I've got a 5V supply from a Minty Boost simulating the 5V from the 'duino. I then have another supply, also grounded to the common ground, thats 14V.
If I pulse 14V onto the "Signal In" port with that powersupply also connected to ground... I get... nothing. The sig-in line goes from 5.08V to 5.6V, and there is no signal on "SigOut".
I've played around with a few variations.. but buggered if I can get this to behave.
Further, if I ground the input signal, I get much better voltage response than if I just ground it to positive... yet this should be designed to read the 12V+ lead off of an injector... The idea is it will take "Signal In" from the 12V+ signal from a Fuel Injector, and then should put out a 0-5V Voltage on SigOut to then read on the Arduino as RPM..
Its driving me nuts... and I refuse to admit defeat with just getting an 8-Pin (eventually) and copying the original schematic... Im guessing now (totally) that my 'test powersupply' is putting 70ma across the base of the 557, which is saturating it. so maybe I need to change the 22k's out ??? I dunno.. I feel well past my depth trying to sort this out...
ARGH!!!! :o :o :-? :-? :-? >:( >:(
Can anyone offer some guidance ? The LM2917's datasheet is at http://jaycar.com.au/products_uploaded/ZL3930.pdf and Its a phillips BC557...