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Detecting Engine's RPM via IR/RF with CAN output

911 Views 5 Replies 5 Participants Last post by  Tony Bogs
Do you know any ready-made or DIY device available in the market, which can detect a running Engine’s RPM (via any IR/RF non-contact method or via Crankshaft sensor) and then via “CAN protocol output” pass-on this RPM value to any of following DC Motor Controller (to control DC Motor’s RPM)?
1. (15B).pdf
2. (13E).pdf
3. OR Any other 200+ Amp DC Motor SPEED & TORQUE Controller (which you will recommend)
Please do let me know if you know any appropriate device?

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· Registered
27 Posts
Discussion Starter · #3 ·
Why are you asking the same question again? Are you now planning for a different design from your previous proposal?
Giving RPM input to a DC Motor Speed Controller

If it is still the old design, the answer is still the same: you don't need to detect the engine's speed. You could possibly read the engine load from the vehicle's CAN bus and send it to a controller by CAN.

Dear Brian, Thanks for your all previous inputs... I am basically a mechanical engineer and so bit confused regarding electronics side. So allow me to compile all my thoughts and concerns here. Hope you can clear following few points:

TARGET: My ultimate target is to run a DC Brushed or Brush-less Motor on 100% same RPM (WITHOUT ANY DELAY) as of Vehicle's Engine RPM (on engine's different loads)

1- Either I can take running Engine's RPM from a Tachometer with RS232 out put or Tachometer with CAN signals out put (which I have not found yet) or with Crank shaft sensor's output voltage. If you have better suggestion then please share.

2- You are saying that I should not be worried about the SPEED/RPM rather I should be more concerned about LOAD/TORQUE of the engine. As far as your this point is concerned the Curtis 1244 DC Motor Controller already handles RPM/SPEED as well as LOAD/TORQUE of the motor. So, do I still need to be worried about syncing LOAD/TORQUE of the Engine with the motor?
if YES, then exactly HOW and with WHICH electronic device I can instruct DC Motor Controller regarding engine's LOAD.

3- If you would be in my place and to achieve above required TARGET, what would be your exact approach?

MY APPROACH (based on current studies, may be it still requires a lot of further input):
1- Detect engine's RPM via Tachometer with RS232 output.
2- Build a RS232 to CAN signal converter (eventually this conversion kit may cause a very little delay in communication (forwarding LIVE RPM value to DC motor controller).
3- RS232 to CAN signals converter will give CAN signals to the DC motor controller.
4- DC motor controller will run the motor on required RPM and LOAD


· Administrator
6,609 Posts
Brian is quite right on this - you are trying to do something that is completely UNNECESSARY in such a way that the whole thing simply will NOT WORK

You should use Torque control - - effectively current control and simply use the tarmac to control the speed

If you were using two motors side by side on a boat your way would make sense - but in a car - NO

For an example look up the old "Twini Minis" - and even a Twini Moke

· Registered
196 Posts
TARGET: My ultimate target is to run a DC Brushed or Brush-less Motor on 100% same RPM (WITHOUT ANY DELAY) as of Vehicle's Engine RPM (on engine's different loads)
Since your motor will be mechanically linked to the engine, it will run at 100% same RPM 100% of the time. It will be impossible for it to run at a speed that is does not correlate unless you add some kind of variable ratio transmission between the electric motor and ICE crank. This is why everybody it telling you to focus on torque, not speed.
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