| ??? 08/14/05 18:19 Modified: 08/14/05 18:23 Read: times |
#99379 - RE : Engine analyser Responding to: ???'s previous message |
Hi Russel , with thanks for your reply
for determining the RPM why do you think you need to sample a signal from the ignition coil primary? You're right , currently i've designed the RPM meter for my DCCS project using a 'Frequency to Voltage'(XR4151) converter , so i was certainly thinking to use the Primary of the Coil ! But this could be helpful , as i said this would be a diagnostic tool , it could report the signal exist in the Coil's primary , this would help in the situation the wires get broken / disturbutor probelm, Etc. he cylinder to cylinder timing is normally fixed mechanically or electrically. in this case this tool could inform the user of possible Egregious differences in cylinder to cylinder timing .or maybe i'm wrong and this type of problem is not possible in engines and maybe if such happens , or in such situations engine donot run at all ? Most of the ones I've seen and used have a split ferrite core that clamps around the spark lead and a number of windings for the pickup coil - a simple transformer. i was planing on such a design , a C and also a I which make a Box around the wire. and some winding on the C side for pickup. For the flash, it is usually a 'ringing choke' style of converter charging a capacitor with about 200-300 VDC and a SCR dumping a small capacitor's chanrge into a trigger transformer for a xenon flash tube. i'll try to find the xenon lights , what i don't know is how to design the 'ringing choke' part ,if you do have a sample design i'll be appreciated . it should be some sort of a step up switching supply. It is normally easier to measure the period between the sparks rather than the frequency. Derivatives with a PCA timer may help here although you have a capture on timer2. Also remember that the angle is a fraction of the period time value. i don't remmember any cheap and available Atmel 8051 derivatives which have a PCA . but there are AVR's available , maybe i'll use one of them ! but it's okay , i could live with the Int+Timer method. I wouldn't waste time using optocouplers - I rarely see use of these in automotive electronics. Best to be careful in pcb layout and protection circuitry. Since the electronics are normally powered from the vehicle electrics, optos add little value. so what you suggest to 'condition' the pickup signal from the Rogowsky Coil ? would this schematic work ? is it good , i really have a feeling which tells me i should use the Opto?? 
Farshid J.H. |
