suzook12 wrote:
OK cool.... So if i put this into radio terms as i'd understand it from my early interest in CB radios and the like (Yeah i know... SAD!!! Lol) the power feed if looked at on an oscilloscope would be like an FM carrier wave with the interference modulated on to it?
If that is the case, i also remeber how ineffective hi and low pass filters were in the day.
i have NO idead about radio waves. lol. im not sure how the interefencce on the carrier wave looks, but on an o-scope, this would like like a large spike. that spike causes chips to shut down, (or destroys them), or causes the same interference that a high power ignition system does, only directly inside the wire, and not via inductance.
Also, if i remember correctly, from my school days and physics in particular, electricity in the real world flows from negative to positive, which would make sense of why earthing to the frame rather than the battery works.
guess that depends on which school you went to! lol. i was taught positive to negative. but its more of a "potential" thing. energy flows are based on the need to balance potential, so a area with negative potential (or ground) can absorb the positive potential from the source. like wise a spot with large positive potential can help bring a negative potenial back up to balance. what really affects it the most, is whats between the two potentials. and of course, when there is no flow, (current) there is no different of potential so power is stored. (ie, if you turn on a large generator but dont connect anything to it, it doesnt make any power) at least, that is how i have always understood it. with Back EMF, the rules arent broken, electricity doesnt "flow backwards" it just happens to be coming from a new source. the coil. and it comes out of that new source with a MUCH higher voltage. and since the ground side is an open, the greatest potential for balance is in the wires, circuitry, and back to the battery. hence the electricity takes the path of least resistance, and it just so happens to be through circuits we dont want it to be. i hope that makes sense, im trying to explain it the best i can as it has been explained to me. (by the USAF lol)
So, in my instance, if moving the earth to the frame doesnt work either entirely or not at all, assuming the cause of my problems is the cause, is there something i could wrap the harness in to shield the wires from inductive interference? Would say something as simple as two or 3 layers of tin foil have any effect if earthed at both ends or would that cause further inductance?
shielding the wire will only help to protect from outside inductance. it does not help with a source "inside the wire" so if you have a large amount of interference coming from a wire, and that wire runs parrellel to a serial cable, then yes, putting shield on the serial wire will help prevent any interference on that wire, but it will not help the original problem. this diode helps the original problem. what happens on motorcycles is that the back emf is so large, and the battery is so small, that the battery cant absorb all of it fast enough so it ends up feeding through the wires themselves, trying to find a load that can absorb it. its not really an inductance problem, although it does cause the same problems with electronics.
Am thinking an oscilloscope would be a usefull thing to have right now, but dont have access to one, but think it would probably shed some light on to cause of interference.
o-scopes are very nice to have. i have a very nice fluke multimeter with built in screen but it stopped working unfortunatly so i had to send it back for repair. hope i get it back soon.
Again, sorry for all the questions
Cheers
Steve
nothing wrong with questions. thats how we all learn and move the game forward.
Im not 150% sure that im entirely accurate, but this is how i understand it so far. im still learning on this subject so bare with me. so far i have found the best results making all the solenoids "power switched" instead of "ground switched" the back emf only happens when the magnetic field around the coil collaspes. that can only happen when the current stops flowing. if the current stops flowing then obviously you have broken the circuit. (via a switch) MOST of the time people make things ground switched, so the side of the circuit that is open back to the source is the power side. (through any electronics or relays it used to get there in the first place) there is only 1 positive potential on the bike and thats the main source for all the electronics so we DONT want to use that. (there is actually 2, but its routed to the battery) By making it power switched you make the path back to the source on the ground side. and there is MANY MANY paths back to ground. with many large "capacitors" along the way (engine block, frame, tires, etc)
Additionally, the best reason to use the ground side is because of the way a alternator or stator works. you have large sine wave, from positive to negative potential and back again. (x3) what this means is that the largest negative potential on the bike is NOT at the negative battery terminal, its actually at the stator housing. (or as close to you can get to it.) that means that this spot in the grand scheme of things can absorb a lot of current very rapidly, making for a good capacitor.
now, we have put a lot of voltage spikes (interference) on the engine block, so we don't want to use that as our reference for digital ground. since its going to be changing potential a lot, we need somewhere cleaner and more steady. so for digital ground, its best to use a ground far away from that, or directly at the battery. if its done right then you will have perfectly clean traces on your data log. also, if your datalogger has a different reference (ground) voltage, than your ecu and sensors do, then your data log will be skewed. for this reason, i tie my datalog ground ( digital reference, NOT the power ground) directly into the ground wire coming off of the TPS circuit BEFORE it goes through the ecu. that ensure that my datalogger and sensors all have the same amount of current flow, and will read identical with no oscillation. and by keeping back emf tied to the engine block ALL of our electronics have clean steady power..
..now.. all that said.. you can just use the diode and not worry about it LOL. some controllers force you to use a ground side switch on solenoids, so in this case you don't really have a choice and all you can do to prevent back emf is use the diode, or use some wiring trickery to switch both sides at the same time. but this locks flyback inside the coil and can cause it to over heat. not to mention its complicated to wire.
anyways.. thats the best grasp i have of the way it all works right now, and so far ive been lucky enough to be able to rid all interference problems.