Low Voltage Variable Power Supply – This project is meant to offer a low price power supply (kitset in most cases) where the official Arduino sketch (for RPi Pico) is supplied to the user who can customize the unit to his requirements.
This unit is currently being superceded to include the Buck-mode step-down voltage converter circuit shown, on the main board. This should allow effective current output measurements, along with the needed smoothed voltage output. It runs on 15V and has an option to approximately double that. Doubling could mean a 30V power supply or a step up module from 15V on the side of the unit. In the visible gap. The step up and step down modules unplug and are easily replaceable.
This unit is currently being superceded to include the Buck-mode step-down voltage converter circuit shown, on the main board. This should allow effective current output measurements, along with the needed smoothed voltage output.
- Rotary switch with 12 positions.
- Small inch square screen though any 3.3V I2C screen should work.
- Rotary encoder with push button.
- 2 Pots
- Several switches including reset. These have alternate connection as jumpers for a remote switch.
- Output for large numeric display, that can be daisy chained.
The board also has Fram memory. There are also a number of voltage measurement circuits, which make use of an ‘analogue in’ chip (74HC4051). This could be superceded by an optical device if accurate analogue voltage multiplexers of this type exist.
It is expected that once a user interface function has been designed, that the board may be reduced (or modified) in complexity.
Microtron is open to negotiation about about how this project can be further developed, with the possibility of marketing to people who require flexibility and possibly voltages up to 30-40V. Remote triggering of current measurements and logging of data (and I2C date/time module data) is a possibility, using the alternate header switch inputs. One problem is that at higher voltages more PWM bandwidth/resolution is likely to be needed. The project could include the following key aspects:
- Determining appropriate specifications for an input power supply.
- Determine operating current and voltage limits. Determine if thicker copper is needed. Review minimum distances between tracks.
- Apply these operating limits in code.
- Design a user interface and allow the user to set a wide range of parameters.
- Design a housing and physical presentation of the user controls.
- Investigate the trade-off between frequency and resolution.
Most of the recent work on this device has been to ensure that the optocoupler is fully activated and deactivated by the PWM signal and that the MOSFETs switch correctly. Some very preliminary load testing has occurred and the incorporation of the Buck mode step down voltage smoothing has yet to be tested.
It is also possible to use the Fram memory socket to plug into an external add-on board that houses I2C devices, like a real time clock with battery.
I originally was aiming for about 0-100V range, however I found it difficult to get components with the necessary ratings. Also adequate isolation of higher voltage measurements from the MCU circuitry was not straight forward. Another aspect was getting enough PWM resolution for such a wide voltage range.
- MCU units with sensors and datalogging.
- Break out boards with user interface. Suitable for datalogging and interactive function including stepper motors.
- Break out board customizations. Sensors, stepper motors, WiFi, SD cards and Fram.
- Design of circuit boards, including design of circuit boards that are a customization of a break out board pilot project.
- WiFi and server collection of data.