I am trying to read status from my heat pump but the heat pump status is driven by a 28vac signal. Anybody have a good solution? Last ditch effert will by to install 28vac relays at the source.
I am trying to read status from my heat pump but the heat pump status is driven by a 28vac signal. Anybody have a good solution? Last ditch effert will by to install 28vac relays at the source.
Hello Milo,
This is a simple solution:
Here's a link to the schematic.
The output will be a rectified sine wave, the capacitor prevents the voltage from dropping fast while the diode is not conducting, the 1MOhm resistor takes care that the input voltage will return to zero. The values here are for a 5V digital input.
Edit:
- The high ohmic values were chosen to prevent damage to your device in case of failure of a solder joint; with 100kOhm in series, protection diodes on the input of your device (ESD protection) will start conducting, and will only have to carry a few microamps. They're not meant for this abuse, but it makes this circuit 'safer' than if you're using lower value resistors.
- if you're very picky about electronics, you could use a schmitt-trigger gateschmitt-trigger gate to prevent floating inputs (place it between the output of this schematic and your input). For most cases, this would be overkill.
Hello Milo,
This is a simple solution:
Here's a link to the schematic.
The output will be a rectified sine wave, the capacitor prevents the voltage from dropping fast while the diode is not conducting, the 1MOhm resistor takes care that the input voltage will return to zero. The values here are for a 5V digital input.
Edit:
- The high ohmic values were chosen to prevent damage to your device in case of failure of a solder joint; with 100kOhm in series, protection diodes on the input of your device (ESD protection) will start conducting, and will only have to carry a few microamps. They're not meant for this abuse, but it makes this circuit 'safer' than if you're using lower value resistors.
- if you're very picky about electronics, you could use a schmitt-trigger gateschmitt-trigger gate to prevent floating inputs (place it between the output of this schematic and your input). For most cases, this would be overkill.
