10 cent tuning - making it pressure-dependent - who can help?

hello
I have been following the forum (heschel, heschel) for some time now, and I must first express my praise. It is truly very informative and helpful. Also, the level of discussion is quite high, which is not the case in every forum - probably due to the questions asked during registration .
Sometimes, the answers could be more helpful and less dismissive, especially in areas where people may lack knowledge.

Okay, so now for my 'problem': I'm thinking about building a 20-cent tuning. I want to connect a boost pressure sensor to the 10-cent tuning, meaning the resistors should only be activated when a certain pressure is reached (apparently the principle behind Authal boxes, see the relevant thread). Ideally, it would be even better to have a multi-stage activation of different resistors.

'I already have a pressure sensor. However, it only operates with a 5V voltage. It outputs a voltage of approximately 1V to 4.5V at the signal output (e.g., at 0.5 bar, it outputs about 2.8V).'
I also have a general idea of how to convert the signal into an on/off signal. It seems like it involves an optocoupler (?), possibly with a potentiometer – at least, I have a small circuit in front of me that appears to be used for something similar.

'Now, how can I best reduce the voltage to a constant 5V? Would a simple fixed voltage regulator before the pressure sensor work (e.g., an LM78xx)?'

I'm not an electrician or anything like that, just a technician in mechanical engineering and a car mechanic, so please don't be too harsh and try to explain things as simply as possible. However, I am willing to learn .

It would be great if something like this could be developed for the general public.



ixery

ps: I would like to use a separate boost pressure sensor to enable a quickly detachable power box.

Hi.

Having a 7805 before the pressure sensor is fine. However, to counteract its tendency to oscillate, capacitors should be placed between the input and output, and between each of them and ground (e.g., standard electrolytic capacitors of 47-220 µF).

I would place an impedance converter after the pressure sensor and use its output to supply the inputs of two optocouplers via resistors to be determined: higher pressure --> higher input current for the optocouplers.
Connect their outputs in an antiparallel configuration, add a variable resistor in series with them (to limit the maximum voltage boost), and connect the whole thing between cable 2 and cable 3.
This basic framework should, in my opinion, be functional and even provides a smooth transition between normal operation and increased fuel injection.

Hi,

I've had that idea before too. Has anyone ever tried it?
The question is, which type of optocoupler is best to use.
There are indeed specific ones for analog signals.
How about optocouplers with a FET output? Would one be sufficient, or do they also struggle with AC signals?
Ulf, how much current do you estimate will flow through the optocouplers?

Regards,

Eike.

eike wrote:

What about optocouplers with a FET output?

Could one be sufficient, or do those also not work with AC power?

Quote:

Hi Eike, If you find something suitable with a FET output (I have no idea what might be available), it might be possible to get by with just 1 optocoupler. However, I think it's safer to use 2 optocouplers connected in anti-parallel on the output side.

Ulf, wie hoch schätzt Du den Strom ein, der über die Optos fließen wird?}

The measurement signal is, as far as I know, 5 volts peak-to-peak, which corresponds to 1.8 volts RMS.
With a 220 Ohm resistor in series with the OTPO, a maximum of approximately 8 mA of current should flow.