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For any add-on boards such as VR conditioners, optos and OEM interface boards
By Rocket
#51975
I have 12V hall sensor, what optimal way to convert signal to 5V ? I found this simple circuit https://speeduino.com/wiki/images/8/83/Highvolthall.png . Does anyone use it ? Looking to v0.4.3 circuit pull up for hall is 1k? What diode is recommended in this application? I guess schottky diode is beneficial for fast recovery in this case? Thanks.
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By PSIG
#51989
ImageNote in that Wiki diagram to only use the R1 resistor if testing shows it is needed to fully pull to ground. ;)

An example of using the blocking diodes can be found here, with a photo of his board using the resistors as the jumpers a few posts later. Yes, it works for any signal that pulls to ground and is over 5V. 8-)
By Rocket
#52068
PSIG wrote:
Fri Jul 23, 2021 4:45 pm
ImageNote in that Wiki diagram to only use the R1 resistor if testing shows it is needed to fully pull to ground. ;)

An example of using the blocking diodes can be found here, with a photo of his board using the resistors as the jumpers a few posts later. Yes, it works for any signal that pulls to ground and is over 5V. 8-)
I have assembled vr conditioner board top side with just opto couple, it should work ok with vr jumper configuration? Not sure about jp4 and jp5 jumper, probably set to vr because opto couple has 10k pull up on output.

Edit: Looking to circuit, vr input have 1k imput resistor and opto conditioner have 220oms input resistor, sot 1,2k probably to hi resistance for 12V trigger input
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By PSIG
#52155
Rocket wrote:
Thu Jul 29, 2021 5:11 pm
is diode is write way connected? it work in reverse in this case?
You may be missing the concept. The diagram is correct. The diode simply blocks any +12V from going into Speeduino from the sensor/module, but does not block grounding by the sensor, allowing the 5V from the Speeduino "Hall" jumper to be pulled-down by the sensor. This gives a 5V-0V signal with no signal conditioner board.

So, the Mega processor first sees +5V from the Hall pullup, and then sees 0V from the sensor grounding the 5V through the diode. Making sense?

To be more accurate, the signal is more like 5V-0.8V due to the diode drop. But, that is OK as long as the low part of the signal is below ±1.2V, which is the threshold for the Mega to see it as a low. For the high part of the signal, anything above ±3.3V works.

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