> ## Documentation Index
> Fetch the complete documentation index at: https://instro.nominal.io/llms.txt
> Use this file to discover all available pages before exploring further.
# Power Supply (PSU)
> Using InstroPSU for SCPI-based programmable power supplies
`InstroPSU` provides a unified interface for programmable power supplies. This class is initialized with a vendor-specific driver (`BK9115`, `KeysightE36100`, `RigolDP800`, …), and provides the vendor-agnostic API (`set_voltage`, `get_voltage`, `output_enable`, …).
## Creating an InstroPSU
```python theme={null}
from instro.psu.drivers import SiglentSPD3303
from instro.psu import InstroPSU
psu = InstroPSU(
name="myPSU",
driver=SiglentSPD3303(visa_resource="USB0::0xF4EC::0x1430::SPD3XJGQ806726::INSTR"),
num_channels=2,
)
```
## Supported Vendors
The following vendor is available as a community-contributed driver in `instro-contrib` (install with `instro[contrib]`; see [Contrib drivers](/library/contrib)):
* **Matrix**: WPS300S-series single-channel via SCPI/RS-232 (`MatrixWPS300S`)
If your vendor or model is not listed, see [Custom Driver Development](/library/custom-instruments#power-supply-psu), or open a [Driver Request](https://github.com/nominal-io/instro/issues) issue on GitHub.
## Example
More examples found in [Examples](examples/psu/index)
## Details
The following presents details about the `InstroPSU`. Specific driver details can be found on [their pages](#supported-vendors).
### Driver Composition
An `InstroPSU` is built from a concrete driver:
```
InstroPSU("name", driver=BK9115(visa_resource="USB0::..."), num_channels=1)
```
* The **vendor driver** (e.g. `BK9115`) owns the connection setup and vendor-specific command mapping.
* **`InstroPSU`** owns the category-level workflow: measurements, commands, publishers, the background daemon.
### Lifecycle
The typical InstroPSU workflow:
1. **Construct**: instantiate the vendor driver and pass it to `InstroPSU`.
2. **`open()`**: establishes the VISA connection.
3. **Configure and measure**: set voltage/current limits, enable outputs, read measurements.
4. **`start()`**: begins a periodic background daemon. (Optional)
5. **`stop()`**: ends the background daemon (if started).
6. **`close()`**: disconnects from hardware.
### Init from a Config File
`InstroPSU` can also be constructed directly from a JSON config file, which removes the need to write any Python setup code:
```python theme={null}
from instro.psu import InstroPSU
psu = InstroPSU(config="bench_psu.json")
```
Where `bench_psu.json` contains:
```json theme={null}
{
"version": 1,
"instrument": "InstroPSU",
"device": {
"name": "bench_psu",
"description": "Bench channel 1 supply",
"manufacturer": "B&K Precision",
"model": "9115"
},
"driver": {
"name": "BK9115",
"num_channels": 1,
"connection_type": "visa",
"visa": {
"visa_resource": "USB0::0x2A8D::0x0101::MY12345::INSTR"
}
},
"timing": {
"poll_interval": 1.0
},
"publishers": [
{
"type": "NominalCorePublisher",
"dataset_rid": ""
}
]
}
```
See [Config Files](/library/config-files) for the full field reference.
### Simulated Power Supply
For development and testing without physical hardware, Nominal Instrumentation includes a local SCPI power-supply simulator. See [PSU simulator](/library/simulated-instruments#psu-simulator) for the quickstart, usage notes, and supported command set.
## Custom Driver Development
For more information on writing a custom driver, see [Custom Driver Development](/library/custom-instruments#power-supply-psu).