Noggin
Member
There's a guy that did an engine swap in a car. The new engine has 3 pickups on the crankshaft whereas the old engine has just 2.
New: Nissan VQ35
Old: Nissan QR25
The guy wants me to make a circuit that will convert the 3 pulse per rev signal to the 2 pulse per rev signal. I already have a board laid out that uses a micro to read the input and then it will give the appropriate output. I've come up with 3 scenarios and would like to know if any of the 3 are correct. What I don't know is if the signal is mainly a duty cycle thing, or if its a pulse count, or if it is timing between pulses.
1. Read first two pulses on input and mirror them to the output. Ignore third pulse.
2. Read pulse high time and low times. Multiply high time and low times by 1.5 (almost the same as 1, just that the pulses are evenly spaced)
3. Measure asserted time period, output asserted time period as a pulse with 2/3 of the length
If the signal comes from the pickup, it would make sense that the overall time that the signal is asserted in any given time period remains constant. The faster it spins, the shorter the asserted period but the less time until the next pulse arrives. Given this, I would assume that the tach is not driven directly from the pickup sensors but electronically, maybe based on simply the time period between pulses. If this is right, it seems that option #2 has the best chance of success.
New: Nissan VQ35
Old: Nissan QR25
The guy wants me to make a circuit that will convert the 3 pulse per rev signal to the 2 pulse per rev signal. I already have a board laid out that uses a micro to read the input and then it will give the appropriate output. I've come up with 3 scenarios and would like to know if any of the 3 are correct. What I don't know is if the signal is mainly a duty cycle thing, or if its a pulse count, or if it is timing between pulses.
1. Read first two pulses on input and mirror them to the output. Ignore third pulse.
2. Read pulse high time and low times. Multiply high time and low times by 1.5 (almost the same as 1, just that the pulses are evenly spaced)
3. Measure asserted time period, output asserted time period as a pulse with 2/3 of the length
If the signal comes from the pickup, it would make sense that the overall time that the signal is asserted in any given time period remains constant. The faster it spins, the shorter the asserted period but the less time until the next pulse arrives. Given this, I would assume that the tach is not driven directly from the pickup sensors but electronically, maybe based on simply the time period between pulses. If this is right, it seems that option #2 has the best chance of success.