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By gkar47
#198161
I’ve got a problem with an electronics project that I’m trying to solve.

I am trying to get a circuit board to pass a signal to a WAV Trigger board. The signalling circuit board is signalling an event by changing a pin’s voltage from 2.46V to 4.72V.

Any idea how I can connect this circuit board to the WAV Trigger's trigger pin? I’m assuming I have to somehow change the 4.72V to 5V for this to work. Does the fact it only goes down to 2.46V, rather than 0V, in non-signal mode an issue?

I've tried connecting them as is and cannot get the WAV Trigger to actually react to the signal from the first board.

I'm a complete noob with electronics.
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By exeng
#198178
Watch the video herehttps://learn.sparkfun.com/tutorials/wa ... 1504673727 and look that the schematic here https://cdn.sparkfun.com/datasheets/Wid ... er_v11.pdf for clues on how to connect to the trigger inputs. I've not used the WAV Trigger in that configuration but if I understand it correctly the trigger inputs are pulled high normally and when pulled to ground (GND) the trigger is activated. You notice this in how he hooks up the keyboard in the video. So it seems your signal must go low (to common ground) to trigger the board. Also this is 3.3V device so I would never drive any input higher than that.

Robertsonics is very good about monitoring any WAV trigger questions. So I would expect him to comment.
By gkar47
#198180
Thank you exeng for your response.

But, the trigger pin can be triggered on high or low depending on the configuration file. I have configured it to be trigger on going high. The documentation also specifies that it can be run on a 3.3V or 5V signal. Also the example in the documentation gets you to test a configuration by connecting the 5V to the pin to simulate an IC 5V signal. So a 5V signal should be fine.
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By exeng
#198183
I stand corrected. As I said I've not interfaced with the WAV Trigger in that configuration. Everything I do is though the serial interface.
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By robertsonics
#198192
You can use a voltage, rather than a contact closure, to activate a trigger by setting the trigger's "hardware interface" to "Active". However, according to the STM32F4 data sheet, any voltage over about 0.3V will be considered "high", so you must switch between a voltage less than 0.3V (low) to anything between 0.7V and 5.0V (high) for this to work. Hope this helps.
By gkar47
#198197
So if I understand my electronics correctly, I should just need to add a resistor to the signal line to pull the 2.46V value down below 0.3V and then the 4.72V value will be about 2.5V, which is in the 0.7-5V range for this to work?
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By robertsonics
#198203
Not sure how that would work - not saying it won't, but I can't immediately see how a resistor will produce the correct voltage swing. My first inclination would be to use a voltage comparator, which would produce a full voltage swing from 0 to 3.3V (or 5V) around an adjustable reference voltage. I can't help design custom circuits, but implementing a comparator circuit should be something you can research on line. Perhaps someone here will have other suggestions.
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By exeng
#198204
Perhaps you can share a bit more about the circuit board the you are trying to create to help the forum understand what the "real world" trigger is. That is, a final stage that swings a voltage from GND to 5V should be easy but what is the stimulus or logic that causes the need to trigger the WAV trigger? I assume you are not using a micro-controller and trying to do something with discrete logic?
By gkar47
#198208
Thank you robertsonics. I'll look into that.

exeng, I have a project which has a circuit board that activates some lights and does some flashing. One pin of the IC chip on this board, that is currently not connected to anything on the board, signals when the circuit is activated. I was told by the creator of this board that the pin will go high on activation. So I tested the voltage on this and found that when inactive it seems to "idle" at 2.46V. When I trigger the board to make the lights flash it raises the voltage to 4.72V. I want to use this trigger to add sound to this project by having it trigger the pin on the WAV trigger sound card. I hope that explains better what I am trying to do.
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By robertsonics
#198210
I'd suggest putting a pull-down resistor (say 10K to ground) on the output and see if that causes the "low" state to go to 0V. It may simply be floating when not being driven the "high" state.
By gkar47
#198452
Well just a final note to let everyone know how I solved my problem. I tried the resister to drop the voltage. That didn't work. I tried a pull down resister, assuming the 2.46V was a floating voltage. It wasn't and that didn't work. What finally did work was using a voltage divider circuit using r1 = 53 ohm and r2 = 470 ohm to bring the low voltage to 0.246 and the high voltage to 0.472. These straddled the 0.3 V low voltage trigger. It seems to be working reliably. I didn't want to try the compactor circuit as I had VERY limited space and wanted to keep this as simple as possible. Thank you robertsonics for the information on the key trigger information that allowed me to find a solution. It might be useful to add that information to the documentation for the WAV Trigger board.