so, the full story. I have another topic here on how to detect a square wave signal +12v/-12v. That topic is solved, I received a lot of great suggestions.
However, The full story is that once I detect that the 12v/-12v 1Khz square wave signal a car ECU generates stopped, I want another device (arduino) to take over the ask from the ECU and to generate similar +12v/-12v signal - at 1Khz, duty cycle is 50%.
As I know, it is not possible to generate negative voltage with arduino - is there anyone who knows how to make such a signal?
For how long time will this second controller have to be generating its +/- signal?
I think about tapping that +/-12 volt into suitable capacitors and use those stored voltages for outputting voltage, not current.
Do you have access to +12V and -12V supplies?
You could use PVT312 opto isolators to switch the 2 supplies to the output.
(Or PVT212, PVT412, depends on how much current is being switched) https://www.mouser.com/Search/Refine?Keyword=pvt312
...and... why would a car circuit generate negative signal voltages? It's sounds terribly wasteful of resources, because it's not (as you are discovering) very easy.
Do you have any links that could educate us about your ECU signals to better answer your question?
...and... why would a car circuit generate negative signal voltages? It's sounds terribly wasteful of resources, because it's not (as you are discovering) very easy.
Do you have any links that could educate us about your ECU signals to better answer your question?
it is the pilot signal every electric car needs to provide through the J1772 connector to command the charger to supply charging.
Tiborx8:
the negative ground wire is also coming from the ECU, just like the positive wire.
Sorry, That make no sense, at all. Where are you measuring the voltages? Between which two points for each measurement.
You have a signal wire and a ground wire. Or do you have two signal wires and a ground wire. Or do you have a single wire that alternates voltages when referenced to a common or ground wire.
Paul
This might be of interest. I followed the other thread and never did convince myself y’all were actually talking about a +12/-12 with respect to ground (0) volt signal, seemed odd.
In their other thread the OP is adamant it's a signal that goes indeed all the way from +12 to -12 and is at 0V when there's no signal. Odd, but for lack of other ways to confirm it (such as tecnical datasheets of the ECU in question) I'll take their word for it.
The circuit from the instructable in #12 looks simple enough to me. The only question I have is... why would you even want to fake this signal?
A +/- 12 volts signal from a device in a vehicle electrical system could simply be derived from an H bridge or similar. The output would look like -12v 0v +12v on an oscilloscope. To recreate it, if required, another H bridge.
A 1 kHz square wave at ±12 volts generated by the EVSE on the control pilot line to detect the presence of the vehicle, communicate the maximum allowable charging current, and control charging begin/end
for the charging system.
I did find one link to the service manual for the year make model but they want 29.99USD, not happening.
Yes, it is possible to generate a +/- 12V signal at 1Khz using an Uno and some external components.
The specific mention in that article of +/-12 volts, -12 volts and 0 volts convinced me it was a competent exposition of truth.
About an H bridge, I basically understand using it for greater peak to peak voltage, and have done similar things with two i/o lines for “AC” excitation of piezo discs. But
will an H bridge ever yield a negative voltage measured wrt to ground?
The hacks I’ve come across so far use DC/DC converters to develop +12 and -12 volts.
