# Closed loop lambda control in fuel injection

#### lotus_mary

Nov 23, 2020
3
Hi, I got a project and I have no idea what to do...I have to do a diagnostic circuit of a lambda closed loop fuel injection that has the corect fill factor of the signal from the lambda sensor : 40%÷60%.

Under 40%, the engine will work on poor mixture and will set a code of 2 digits(between 40...49)

Over the 60%, the engine will work on rich mixture, and will set another code, different from the first one (still between 40...49).

The signaling of the emergency situation will be done with a signaling lamp with 1 Hz frequency and a 0.5 filling factor.

- I have to use a microcontroller, make a proteus simulation, and solve this using functions in C

Until now, I only understood what closed loop lambda is, found some theories in general and learned that 16 bytes microcontrollers are best for engines applications, but I really don't know how to do the circuit or the code....I don't have any knowledge about power electronics or automotive, just some C/C++ and some basic electronics. Any help is useful. Thank you!

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,176
Your description is a bit meager, lacking information.

From your description I take it that you don't have to take care of the closed loop control at all.
The engine gives you a diagnostic code (2 digits). All you have to do is to evaluate the code and make an LED blink.
I may have misinterpreted your description. If so, please supply more detail.

What is the ominous "filling factor" you mention? IS that what we call duty cycle? If not, please explain.

I have to use a microcontroller
Which one?
learned that 16 bytes microcontrollers are best for engines applications,
If my above interpretation is correct, you will not need a 16 bit µC. However, as you are going to program in C, the word size of the µC is imho irrelevant. You could use 8 bit, 16 bit, 32 bit etc., whatever you are comfortable with.

I really don't know how to do the circuit
Circuitwise all you need is a basic µC circuit (you can find them on the internet, probably you can find ready-to-use Proteus files) and the interface to accept the diagnostic code.

#### lotus_mary

Nov 23, 2020
3
Yes, sorry, I meant duty cycle (I translated word for word)
Ok, thank you, what I wrote is all the information that I received for the project, that's why I think I got complicated unnecessarily, it's just that I haven't done anything like this until now.

Last edited:

#### Harald Kapp

##### Moderator
Moderator
Nov 17, 2011
13,176
I suggest you tackle this task in steps:
1. Define the hardware architecture of the circuit (sounds more posh than it is):
- The main question is: Is the derivation of the 2-digit code from the lambda sensor part of the project or can it be assumed that the code is provided by the sensor?
In the first scenario (% from sensor) you need to create an interface between sensor and µC, possibly using a built-in ADC (analog digital converter) of the µC.
In the second scenario you need to create a digital interface from the sensor's 2-digit output to the µC.
- select a suitable µC. You need one with built-in ADC for the 1st scenario, you'll need one with lots of digital inputs or a serial interface for the 2nd scenario.
2. Create the software architecture of your program (again: sounds more posh than it si):
- Define the program flow like
* get input data (either from ADC or from digital interface)
* process input data
* depending on the outcome of the processing make the LED blink or not.
* repeat
For making the LED blink there are several methods. The 2 in my opinion most common methods are:
1. use delays to alternate between LED on and LED off
2. use a timer unit of the µC to create the blinking effect
Look up the advantages and disadvantages of both methods and decide which one you want to use. Since the task description doesn't contain any hint, any solution that works should be acceptable. In your description you should be able to justify your choice and show that you have researched different methods. This usually impresses your teacher, tutor or whomever.

It is our policy not to provide ready solutions to homework/assignments. We will guide you through the process of finding a solution n your own.

#### lotus_mary

Nov 23, 2020
3
Thank you very much, now I have a clearer idea on what to start with.

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