BobbyZ Posted March 28, 2008 Share Posted March 28, 2008 Technically I don't think that your first picture is a "circuit" the definition that I know requires a path for current. S: (n) circuit, electrical circuit, electric circuit (an electrical device that provides a path for electrical current to flow) The first picture you have has no current running so it is not dropping any voltage. The resistors aren't actually dropping any current either in your example. Yes resistors limit current (when there is current), but they also drop voltage. The LED example is perfect. Once an LED has turned on (forward voltage > 0.7V) I will step through how to choose a resistor for an LED. You need three things: Input Voltage, Voltage Drop of LED, and Current Required. The circuit is shown below. (Nasty schematic drawn in paint on a touchpad, I am on my wife's laptop so I dont have my fancy schematic capture software) E.G. (These are fairly typical) Vin = 5V Vf = 0.7V I = 10mA Voltage Drop across resistor = 5-0.7 = 4.3V Resistance required for current of 10mA R=V/I (Ohms Law Again!!) R=4.3/10mA = 430 Ohms You have to find that voltage drop across the resistor before you can find the resistor to use. There you have it check it here: http://led.linear1.org/1led.wiz if you dont believe me. (There answer is different because they round to the nearest real resistor value that you can buy) I just designed a PCB which required me to drive around 40 LED's and I had to choose the resistors carefully so that the LED's would all turn on and I wouldn't have to mess with my input voltage too much. (0.7V is just an example turn on voltage. The LED's I used on the board above actually had a voltage of 1.1V) Dont forget Ohm's Law... Quote Link to comment Share on other sites More sharing options...
MJLamberson Posted March 28, 2008 Share Posted March 28, 2008 Great info, thanks! Quote Link to comment Share on other sites More sharing options...
Silver Mine Motors Posted March 28, 2008 Author Share Posted March 28, 2008 Ok well i guess i'm going to think about playing with the temp sensor and see how i like it. Thank you guys very much for your extensive input on the topic. i've read it twice so far and i learned somthing new each time. feel free to keep your conversation going! Quote Link to comment Share on other sites More sharing options...
Noddle Posted March 28, 2008 Share Posted March 28, 2008 I've been using this trick for a while, I have a rotary switch connected to my temp sensor, I have 3 positions, rich, normal (straight through), and lean here's a picture on how its wired. Quote Link to comment Share on other sites More sharing options...
Silver Mine Motors Posted March 28, 2008 Author Share Posted March 28, 2008 I really feel stupid, but i don't know whats going on in this picture. Could you talk about it some more. I don't really know much about electronics so keep it in simple terms. Tell me what parts i have to buy. What parts go were. tell me how it's working for you. Maybe draw a picture, that might help me. Thanks noddle Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted March 28, 2008 Administrators Share Posted March 28, 2008 Technically I don't think that your first picture is a "circuit" the definition that I know requires a path for current. Doesn't the DMM complete the circuit? In that circuit, the LED 'see's' 5v. The resistor is only limiting the current. Industry calls that a "current limiting resistor", yes?. Why do they call it that? Because that's what its doing. They don't call it a "voltage limiting resistor" because its not limiting the voltage. Reducing the current, at the same voltage, decreases the wattage, and thats what keeps the LED from burning up. The voltage on one end of the resistor will be lower than the voltage on the other. That statement, on its own, is misleading. In this cuircuit, measure the voltages at each of the red dots, in any configuration you wish and write them down.... Do the same with this circuit.... You'll notice that your voltage readings are exactly the same in each circuit, even though there is 100 times more resistance in the second circuit. Why? Because resistors do not IMPEDE VOLTAGE. However, put an ammeter in line of both of those and you see the total circuit amperage is 1/100 in the second circuit. Why? Because resistors do IMPEDE CURRENT. Resitors impede current. That is their function. That is what the do. Every English written modern textbook says so. Resitors do not impede voltage... not one modern textbook says they do. Quote Link to comment Share on other sites More sharing options...
BobbyZ Posted March 28, 2008 Share Posted March 28, 2008 Doesn't the DMM complete the circuit? I guess technically it does but a voltage meter has an impedance which is virtually infinite meaning there is still no current running in the circuit. In order for a resistor to do ANYTHING it has to have current running through it. In that circuit, the LED 'see's' 5v That is incorrect, if there is current running through the circuit then the LED will "see" whatever voltage is left after the voltage drop across the resistor. This voltage drop across the resistor will change depending on the current. Here is my proof... Voltage at the supply is 5V Voltage at the LED is around 2.8V (Apparently that is the turn on voltage of these LED's, I just had them sitting on my desk so I dont know the specs.) Lets try the old analogy of water verses electricity. The analogous component in water flow is any kind of restriction. If you have water running through a hose and you put a kink in it, it will act like a resistor. The water pressure (voltage) will be lower after the kink than it was before the kink, the water flow (current) will also be lower in the entire hose. However this requires water flow. If you have the same hose with a kink in it but there is a nozzle that is shut at the end so no water is flowing, than the kink wont do anything. It wont reduce the water flow (already zero), and it wont reduce the water pressure. That is what your first circuit showed; no current running means no voltage drop across the resistor. You are completely correct in your evaluation of the circuits you posted most recently. The voltage drop across each resistor is going to be the same becuase you have scaled up your voltage divider (did you hear that "voltage drop across each resistor"). However, this does not mean that they are not dropping voltage. Your statement impede voltage does not make a whole lot of sense. Impede implies some kind of flow. Voltage is not a flow, it is a "pressure" in one sense. (How big of a difference in the number of electrons is there between two points) That is essentially what voltage means. You may not find a single textbook that says "resistors impede voltage". But every single textbook will say that voltage will drop across a resistor. (Specifically they will say that the V=IR) OHMS LAW!!!! Yes a resistor will limit current I agree with that statement, but your other statement that resistors do not drop voltage is incorrect. They drop voltage very well. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted March 28, 2008 Administrators Share Posted March 28, 2008 A pair (or more) of resistors can be used to PROPORTION voltage. That is a voltage divider. That is what you're describing. There is no voltage loss, just a rearrangement. Total circuit voltage will always be the same, regardless of how many resistors are used. And that will be the end of this debate. It is seriously off topic anyhow (not your fault). Quote Link to comment Share on other sites More sharing options...
BobbyZ Posted March 28, 2008 Share Posted March 28, 2008 And that will be the end of this debate. It is seriously off topic anyhow (not your fault). Maybe a little my fault... Truce. Until next time... Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted March 28, 2008 Administrators Share Posted March 28, 2008 Truce. Until next time... May the Force be with you Quote Link to comment Share on other sites More sharing options...
Noddle Posted March 29, 2008 Share Posted March 29, 2008 I really feel stupid, but i don't know whats going on in this picture. Could you talk about it some more. I don't really know much about electronics so keep it in simple terms. Tell me what parts i have to buy. What parts go were. tell me how it's working for you. Maybe draw a picture, that might help me. Thanks noddle One thing, I don't own a "Z", but my system is pretty much the same, it's uses a "Bosch L Jetronic" system. all I'm doing is changing the resistance the ECU reads from the temp sensor. The rotary switch is wired for 3 settings, normal, ie direct connection to the ecu to temp sensor, rich - ecu through a resistors to the temp sensor, and lean, ecu through a resistors to ecu earth (no temp sensor). To work out the resistance, all I did was for lean was, drive the car for 1/2 an hour or so, make sure it was very hot, (hotter than normal driving) ie hill driving, and record the resistance (L1) of the temp sensor, for rich - start the car cold, leave it idling for a minute or so and record the resistance (R1). You need to also record the resistance when the engine is in its normal running temperature (N1) I done this a year or 2 before I got my wide band, so doing the above I though it should be with in a safe limit on my car the lean setting is about 1 and a bit AFR leaner than normal, I can't select this setting until the engine has been running for a few minutes, else it has a nasty dead spot just off idle. I've included a picture that may help The resistance for rich setting would be "N1-R1" , the resistance for the lean would be "L1" I hope this makes sense Nigel Quote Link to comment Share on other sites More sharing options...
Silver Mine Motors Posted March 29, 2008 Author Share Posted March 29, 2008 So basically your temp sensor is plugged in, and you cut the line going to the ecu. Then you put a switch with three settings. One setting just reconnects the wires. The other two also reconnect the wire but they have resistors on them. One question what are we changing in the line of the temp sensor. The volts or amps? Or? Also just to be sure how exactly did you test the resistance in the temp sensor lines? I get the process you did but you used a multimeter right? And you were checking for amps or volts? just to be sure the way to know what the resistance in the lines are at different times in engine temperature is by testing the line that goes to the temp sensor and then testing the line coming out of it and going to the ecu. What ever the difference is, is what you would call n1, l1 or r1 right? Quote Link to comment Share on other sites More sharing options...
Noddle Posted March 29, 2008 Share Posted March 29, 2008 One question what are we changing in the line of the temp sensor. The volts or amps? Or? We are changing the resistance Also just to be sure how exactly did you test the resistance in the temp sensor lines? I get the process you did but you used a multimeter right? And you were checking for amps or volts?I checked the resistance at the temperature sensorjust to be sure the way to know what the resistance in the lines are at different times in engine temperature is by testing the line that goes to the temp sensor and then testing the line coming out of it and going to the ecu. What ever the difference is, is what you would call n1, l1 or r1 right?as I said above I tested the resistance at the sensor, and yes N1,L1 and R1 was the result of those tests. On my engine the resistances gets smaller as the engine warms up. I found my original research for you, http://forums.hybridz.org/showthread.php?t=90063&highlight=fuel+tweek post #7, and this one http://www.atlanticz.ca/zclub/techtips/tempsensorpot/index.html I hope this helps Nigel Quote Link to comment Share on other sites More sharing options...
Silver Mine Motors Posted March 30, 2008 Author Share Posted March 30, 2008 ok now i get it. thank you nigle! Quote Link to comment Share on other sites More sharing options...
Silver Mine Motors Posted April 1, 2008 Author Share Posted April 1, 2008 Ok I made a unit to hook up to my temp sensor. The unit is going to have two settings: rich, lean, and original. I’ll take some pictures tomorrow. I have one last question. Today I went to look at the car and I noticed there were two temp sensors and one smaller sensor with just one wire coming out of it. The other two sensors had two wires each. My question is which one of the two sensors is the one I have to connect the adjustable unit I made to. Just tell me which sensor to connect it to in terms of the sensor closest to the passenger side (right) or the sensor closer to the driver’s side (left) of the engine. If you look at them you will notice one is closer to the left and the other one is closer to the right. Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Administrators RTz Posted April 1, 2008 Administrators Share Posted April 1, 2008 The one with the single yellow wire is the temp. 'sender'. Its only function is to provide a signal for your temp. gauge. It has no bearing on the EFI system. Quote Link to comment Share on other sites More sharing options...
cjames Posted April 1, 2008 Share Posted April 1, 2008 Ok I made a unit to hook up to my temp sensor. The unit is going to have two settings: rich, lean, and original. I’ll take some pictures tomorrow. I have one last question. Today I went to look at the car and I noticed there were two temp sensors and one smaller sensor with just one wire coming out of it. The other two sensors had two wires each. My question is which one of the two sensors is the one I have to connect the adjustable unit I made to. Just tell me which sensor to connect it to in terms of the sensor closest to the passenger side (right) or the sensor closer to the driver’s side (left) of the engine. If you look at them you will notice one is closer to the left and the other one is closer to the right.Thanks in advance. Check the link to Atlanticz that Noddle posted a few threads up, it details what wires and what sensor you need to play with. Quote Link to comment Share on other sites More sharing options...
cjames Posted April 1, 2008 Share Posted April 1, 2008 Ive thought of a few variations to this also. If the pot, or resistor of choice were wired in parallel with a normally closed switch in the stock wiring, some different things could be achieved. A switch placed somewhere on the throttle linkage could activate the resistor circuit only at a certain throttle position (like WOT). Or for the turbo crowd, a pressure switch that opened at a certain boost level would enrich the mixture only on boost. With the switch closed, the signal would chose the path of least resistance, and go straight from the water temp sensor, through the switch, to the ecu. When it is opened, the signal to the ecu would have no other path than through the pot or resistor. When I get the turbo engine built and installed, I'll try this if I need more fuel on boost. If anyone else has done this, I'd love to hear the results, but I see no reason why it wouldn't work. I'd include a drawing if I knew how to post one. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted April 1, 2008 Share Posted April 1, 2008 How much more duty cycle do you guys think you will get? Quote Link to comment Share on other sites More sharing options...
Silver Mine Motors Posted April 1, 2008 Author Share Posted April 1, 2008 wait so the only way to lean out my ratio is by manually adjusting my afm? Quote Link to comment Share on other sites More sharing options...
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