IAN CANADA PurePi II 5V + 3.3V Ultracapacitor Lifepo4 Battery Power Supply Combo User Manual

IAN CANADA PurePi II 5V + 3.3V Ultracapacitor Lifepo4 Battery Power

Supply Combo

Introduction

The PurePi PurePi II is a power supply combo designed for Raspberry Pi. It consists of a 5V ultracapacitor power supply and a 3.3V isolated pure LifePO4 battery power supply. It provides a stable and reliable power source for your Raspberry Pi projects.

Features and Specifications

• 5V ultracapacitor power supply with two 100F/2.7V ultracapacitors pre-installed. ESR less than 10mOhm.
• 3.3V isolated pure LifePO4 battery power supply with battery holders pre-installed for two 18650 battery cells. ESR less than 6 mOhm.
• Special designed gold-plated spring contacts to power a Raspberry Pi directly to the GPIO from the bottom side of the PCB without needing any connectors.
• Works as a seat base for the whole project. Anti-vibration spike feet and rubber ring suspensions can be installed.
• Only one standard 5V 2.5A or higher current power supply in USB-C is needed as power input.
• On-board power ON/OFF control switch. This switch can also be extended as an external ON/OFF switch.
• Remote ON/OFF control output signals make it possible to integrate with multi-power supply systems as a group to perform a master on/off control.
• Built-in protection scheme to prevent battery cells from being exhausted or having low output voltage.
• Passive power supply with ultra-low noise and high dynamic current.
• Ultra-low ESR MOSFETs are controlled by optical isolators to eliminate any possible leakage current.
• Built-in active balancers for ultracapacitor protection.
• Low cost but no compromise on performance.
• DIY friendly.

PurePi II’s new improvements

• Adds a powerful SYNC charging function. Can recharge the battery cells during music stops, extending battery pure time and avoiding output voltage drops or triggering the protection mode even during long music sessions.
• SUPPORT USB-C new PD protocol.
• It no longer blocks the SD card of the Raspberry Pi. The external ON/OFF control connector has been moved to a new location.

Kit includes:

• PurePi or PurePi II (fully finished with ultracapacitors and battery holders pre-installed)
• 4 of M2.5*7 mm standoffs
• 4 of M2.5 screws

Getting started

1. Install the 4 supplied 7mm standoffs to the PurePi.
2. Install Raspberry Pi on top of the PurePi through the 7mm standoffs and then 4 11mm standoffs to fix it at the position. Make sure the five spring contacts are connected to the GPIO pins properly at the bottom side of the Raspberry Pi.
3. Install a FifoPiMa (or a FifoPiQ7, or other audio HATs) on top of the Raspberry Pi properly. Use two good quality wires to connect the pure 3.3V battery power output from J2 of PurePi to J5 of FifoPiMa. Please be very careful not to reverse the positive and negative terminals.

5V + 3.3V ultracapacitor/LifePO4 battery power supply combo for Raspberry Pi

Introduction

• PurePi is a compact-size audiophile grade dual power supply combo that is specially designed for Raspberry Pi audio applications to improve sound quality.
• PurePi integrates a 5V ultracapacitor power supply and a 3.3V isolated pure LifePO4 battery power supply together in one PCB. With the spring contacts, it is very easy to install a Raspberry Pi and other audio HATs on top of the PurePi without needing any additional power connectors.
• PurePi can also be used as a seat base of the whole audio project with anti-vibration spike feet and possible rubber ring suspensions.
• PurePi would be very suitable for building FifoPi or FifoPiMa-based Raspberry Pi stream transports, DACs, and other audiophile projects.
• PurePi is functionally equivalent to a ConditionerPi 5V plus a LifePO4Mini 3.3V.
• PurePi II is an improved version of PurePi with some new features.

Features and Specifications

• 5V ultracapacitor power supply with two 100F/2.7V ultracapacitors pre-installed. ESR less than 10mOhm
• 3.3V isolated pure LifePO4 battery power supply with battery holders pre-installed for two 18650 battery cells. ESR less than 6 mOhm. The ultra-low output noise would be only decided by the battery cells.
• Special designed gold-plated spring contacts to power a Raspberry Pi directly to the GPIO from the bottom side of the PCB without needing any connectors
• Works as a seat base for the whole project. Anti-vibration spike feet can be installed. The rubber ring suspensions are also possible to be installed.
• Only one standard 5V 2.5A or higher current power supply in USB-C is needed as power input.
• On-board power ON/OFF control switch. This switch can also be extended as an external ON/OFF switch.
• Remote ON/OFF control output signals make it possible to integrate with multi-power supply systems as a group to perform a master on/off control.
• Built-in protection scheme to prevent battery cells from exhausted or low output voltage
• Passive power supply with ultra-low noise and high dynamic current
• Ultra-low ESR MOSFETs controlled by optical isolators to eliminate any possible leakage current
• Built-in active balancers for ultracapacitor protection.
• Low cost but no compromise on performance
• DIY friendly

PurePi II’s new improvements

• Add a powerful SYNC charging function. Can recharge the battery cells during the music stops. This feature will be a great help to extend battery pure time and to avoid the output voltage drop or trigger the protection mode even if you listen to music for a very long time. The SYNC control signal can be connected from the J5 of MonitorPi Pro or the MUTE signal of a FifoPiQ7. The PurePi II SYNC input has an on-board optical isolator so it doesn’t affect the performance at all.
• Support USB-C new PD protocol
• No longer blocking the SD card of the Raspberry Pi, the external ON/OFF control connector was moved to a new location.

Kit includes:
PurePi or PurePi II (fully finished with ultracapacitors and battery holders pre-installed)

• 4 of M2.5*7 mm standoffs
• 4 of M2.5 screws

DIMENSIONS

Layout and Dimensions (in mm)

Getting started

1. Install the 4 supplied 7mm standoffs to the PurePi.
2. Install Raspberry Pi on top of the PurePi through the 7mm standoffs and then 4 11mm standoffs to fix it at the position. Make sure the five spring contacts are connected to the GPIO pins properly at the bottom side of the Raspberry Pi.
3. Install a FifoPiMa (or a FifoPiQ7, or other audio HATs) on top of the Raspberry Pi properly. Use two good quality wires to connect the pure 3.3V battery power output from J2 of PurePi to J5 of FifoPiMa. Please be very careful not to reverse the positive and negative terminals.
4. Install a TransportPi MkII (or HdmiPi, HdmiPi Pro, TransportPi AES) on top of the FifoPiMa using 4 13mm standoffs. Connect the supplied U.FL cable from the FifoPiMa MCLK output socket to the J4 MCLKIN of TransportPi. Install a MonitorPi into the AUX GPIO of FifoPiMa if you need an OLED display (optional).
5. Install two 18650 3.2V LifePO4 battery cells into the battery holders at the bottom side of the PurePi. Please be very careful not to reverse the battery cells.
6. Make sure S2 is in the OFF position. Connect a standard 5V USB-C power adapter with 2.5A or higher rated current to DC input J8 of the PurePi. The DC input indication LED D11 will light up shortly, or flash for a while before light up.
7. If it is the first time using the PurePi from empty, please wait for a couple of hours until UC FULL LED D10 and BATTERY FULL LED D4 are both lit up. Then turn the power switch S2 to the ON position. POWER ON LED D1 and UC enable LED D13 and PURE battery LED D8 will be all lit up.
8. Make sure everything is configured properly as required.
9. Enjoy the music.
10. Turn S2 to the OFF position when finished.

Tips:

1. It’s strongly advised to leave the DC input always connected to J8 so that the ultracapacitors and batteries can be kept fully charged before the next time turned on.
2. If D11 doesn’t light up when the USB power input is plugged in, it means either the USB power cable is too long or the USB power adapter doesn’t deliver enough output current. You can fix the issue by replacing it with a good USB power cable or a good power adapter.
3. Only 3.2V LifePO4 battery cells can be used. Don’t use any other lithium batteries.
4. Both ultracapacitors and batteries can deliver huge currents. Short circuits or reversals can result in serious damage to the PCB and other circuits.

Connectors and switches

J8: DC power input connector in USB-C
A standard 5V USB-C power adapter with than higher-than-rated 2.5A current must be connected to this connector to function.

J4: 5V ultracapacitor power output in spring contacts

• 1, 3: 5V
• 5, 10, 13: GND

This is the main output of PurePi. This output will be turned on and off when the ON/OFF switch is turned on or off. It is designed to connect to the GPIO of a Raspberry Pi directly from the bottom side.

J6: Optional 5V ultracapacitor output in 5mm terminal block
J6 works as an optional backup output. It is internally connected to the same 5V output of J4. This output can be used if the application requires it.

J2: Pure 3.3V battery output in 5mm terminal block
This is the pure 3.3V LifePO4 power output. This output will be turned on and off when PurePi is turned on or off. FifoPi clean side or other high-quality audio devices can be connected to this connector. This output will be 100% isolated in pure output mode when D8 is lit. A fuse F2 is installed to this output to protect from overcurrent or short circuits. The Littelfuse P/N of this fuse is 0451005.MRL

J3: Continuous 3.3V battery output in 2 PIN Molex Mini-Fit connector
This continuous output is specially designed for clock oscillators and many other analog applications that need continuous power for a long time break-in. The continuous output is non-switched, so no matter whether the LifePO4 Mini is turned on or off, the output will be always connected to the LifePO4 battery cells. Unplugging the cable is the only way to disconnect this output from the load. The related Molex P/Ns of the cable are

• Housing : 39012020
• Terminal : 39000038

F2 fuse is also applied to this output to protect from overcurrent or short circuits.

S2: ON/OFF switch

J5: External on/off control switch connector, in 2-pin PH2.0 connector
The external on/off control switch is functionally equivalent to the on-board switch S2. To use the external on/off control switch, On-board switch S2 must be in the off position. External on/off switch is not supplied in the package.

J9: Master on/off control output in 2-pin PH2.0

1. Control signal –
2. Control signal +

To set up a control chain of a power supply group, we can connect J9 to the slave input of the following power supplies through a control cable.

S4: Battery disable switch

• OFF : Battery power function enabled (default)
• ON : Disable battery power function

S4 must be kept at the OFF position in normal operating (default) However if you don’t have batteries installed on PurePi, you have to switch it to the ON position.

J7: External ultracapacitor connector in 2-pin PH2.0

1. Ultracapacitor –
2. Ultracapacitor +

Though it is not recommended if you want to increase the ultracapacitor capacity of a PurePi, you can install an external ultracapacitor pack to this connected. But it has to be very very careful:

1. The external ultracapacitors must have 5.4V or higher rated voltage
2. Both internal and external capacitors have to be discharged (by a 5-20 ohm power resistor) completely before connecting to J4.
3. The pre-charge time of PurePi will be much longer.

J10: SYNC control signal input in 2-pin PH2.0
(PurePi II only)

1. SYNC control signal
2. SYNC control signal +

To enable the SYNC mode, this connector can be connected to J5 of MonitorPi Pro, or control signal + needs to be connected to the FifoPiQ7’s MUTE output, while the SYNC control signal needs to be connected to the FifoPiQ7’s clean side GND. With a built-in isolator, this control signal is nonpolar and will be optically isolated from any external devices.

LED indicators

• D11: Power INPUT GOOD indicator. When lit, it indicates that the power input voltage is applied well and the voltage is higher than 4.9V.
• D1: Power ON indicator. Indicating that the PurePi is turned on and output voltages are applied when lit.
• D13: Ultracapacitor enabled indicator. When lit, it indicates that the ultracapacitors are fully charged and applied to the output. If this LED is off when powered on, it means that the voltages over ultracapacitors are not enough to be enabled for output. They still need to be charged more.
• D8: Pure battery output indicator. Indicating the battery section is in pure output mode when lit.
• D10: UC FULL indicator. Indicating that the ultracapacitors are fully charged when lit.
• D4: Battery full indicator. Indicating battery cells are fully charged when lit.
• D9, D12: Ultracapacitor unbalancing warning LEDs.

PurePi example projects

1. Advanced compact size ultra-low jitter SYNC mode Raspberry Pi streamer transport

Project components:

1. PurePi 5V + 3.3V ultracapacitor/LifePO4 battery power supply combo
2. Raspberry Pi
3. FifoPiMa (or FifoPiQ7)
4. TransportPi mKII (or HdmiPi, or the coming TransportAES and the HdmiPiPro)
5. MonitorPi (optional)

Configurations: Keep everything as default no change

Connections:

1. Connect the MCLK from J6 of FifoPiMa to J4 of TransportPi MKII.
2. Connect the 3.3V battery power supply from J2 of PurePi to J5 of FifoPiMa with two high-quality wires.
3. Install the MonitorPi into the AUX GPIO of the FifoPiMa (optional)

Note : The spike feet kit can be found at Amazon.

Low-cost high-performance audiophile master mode RaspberryPi streamer transport

Project components:

1. PurePi 5V + 3.3V ultracapacitor/LifePO4 battery power supply combo
2. Raspberry Pi
3. TransportPiDigi all-in-one master mode RaspberryPi transport HAT

Configurations:
Remove jumpers from J2 of TransportPiDigi to use PurePi’s 3.3V battery power supply.

Connections:
Connect the 3.3V battery power supply from J2 of PurePi to J3 of TransportPiDigi with two high-quality wires.

Note: MonitorPi can also be installed into the GPIO of the TransportPiDigi as an option if you need an OLED display for this project.

ESS DAC in SYNC clock mode with balanced/SE transformer I/V

Project components:

1. PurePi 5V + 3.3V ultracapacitor/LifePO4 battery power supply combo
2. Raspberry Pi
3. FifoPiMa (or FifoPiQ7)
4. ESS9028Q2M DAC HAT
5. Transformer I/V board with two LL1544A audio line transformers
6. ESS controller

Configurations:
Configure ESS9028Q2M DAC to SYNC mode to use FifoPi’s low jitter MCLK at SYNC mode Keep everything else as factory default with one change

Connections:

1. Connect the MCLK from J6 of FifoPiMa to EXT MCK input of the ES9028Q2M DAC.
2. Connect the 3.3V battery power supply from J2 of PurePi to J5 of FifoPiMa with two high-quality wires.
3. Connect the 3.3V battery power supply from J2 of PurePi to J3 of ES9028Q2M with another two high-quality wires (share the 3.3V battery power supply).
4. Install the ESS controller into the AUX GPIO of the FifoPiMa.

Note : Can also use ES9038Q2M Dual Mono DAC HAT.

Application notes

Safety notes
Once charged, the ultracapacitors will store energy even if PurePi is switched to the OFF position. Please be very careful during installation not to short the circuit, especially when using metal tools.

Where can I buy the spike feet?
Spike feet kit can be found at Amazon. You can just search “Spike feet kit”. For example:

How to install the anti-vibration rubber ring suspensions?
Rubber ring suspensions help the XO oscillators improve phase noise performance by reducing mechanical vibration. It is possible to implement this solution on a PurePi. To do so, you will need:

• Break the PurePi PCB from the frame.
• Hook up 4 rubber o-rings (5×2 or similar) between the frame and the PurePi. (O-rings can also be found at Amazon)

Note : Please don’t break the PurePi PCB unless you decide to.

Is it possible to upgrade the performance of this PurePi?
The performance of this PurePi is still possible to be upgraded by integrating with a UcConditioner 3.3V`. You can connect J2 to UcConditioner 3.3 input. In this case, the output has to be connected to the output of UcConditioner 3.3V.

Does the quality of DC input have business with the PurePi output quality?

The pure LifePO4 battery output is 100% isolated from the input at the pure mode. The on-board battery charger will also be disabled in pure output mode. So theoretically the quality of battery outputs will have no business with the quality of the input DC power supply. However, the 5V ultracapacitor output may still have something to do with the DC input because it’s not in isolation mode. A higher-grade DC power supply can still have lower EMI noise to the environment. So, there will be still some improvements if the 5V DC input with a lower noise linear power supply.

Working principle of the LifePO4 power supply section

The lifePO4 power supply section has three operation modes

Pre-charge mode
LifePO4 power supply will work in pre-charge mode when PurePi is off and the input 5V DC input is still connected. In this mode, the battery cells will be connected to the onboard battery charger. The full LED D4 will be lit if the batteries are fully charged.

Pure output mode
LifePO4 output will go to the pure output mode if PurePi is turned on while the full LED D4 is lit. In this mode, only the batteries will be connected to the outputs. The charger and all other circuits will be disabled and disconnected from the output. All the monitoring and controlling jobs will be performed through the optical isolators. So the outputs will be 100% isolated from the rest of the circuits. Pure LED D8 will be lit to indicate the LifePO4 section is running in the pure output mode.

Protection mode
Because only the batteries will be connected to the load, after running for a very long time in pure mode, the battery cells can be exhausted. In this case, to protect the batteries from damage, a protection mode will be triggered. The CC-CV charging circuit will be connected again to recharge the battery cells. The output doesn’t stop in this protection mode but the low noise performance will be degraded slightly (active circuits involved). After battery cells get fully charged again, the LifePO4 output will be automatically switched back to the pure output mode.

Note : The batteries will be disconnected from the PurePi by the relay when the input power is absent. The switched output J2 will be also off in this case. However, the continuous output J3 will still be connected to the battery cells without stopping.

How to enable the new SYNC charging function
The SYNC charging function was disabled by default. To enable this feature, you just need to connect the SYNC control signal form to J10 of PurePi II from J5 of MonitorPi Pro or the MUTE/GND signals of a FifoPiQ7. After that, the LifePO4 battery cells will be re-charged when music is stopped or paused .

Can a PurePi work for RaspberryPi Free applications
Yes, PurePi works for Raspberry Pi-free applications. For example, a full- function DDC project or multi-input DAC project. You will need a GPIO pin connector (sold separately) to be installed between PurePi and the first board of the stack, such as a ReceiverPi Pro or ReceiverPi DDC. Also, you will need 12mm standoffs for a ReceiverPi Por of 15mm standoffs for ReceiverPi DDC.

History of revising

• Jul. 12, 2022, V0.9b released
• Apr.15.,2023 V1.0 released fixed typing mistakes
• Aug. 30, 2023, V2.0 was released for PurePi II

© 2022 Ian Jin. The firmware code embedded in the PurePi is the property of Ian Jin. You are granted a non-exclusive, non-transferable, non-sublicensable, royalty-free right to use the PurePi solely for your own, non-commercial purposes. You may not distribute, sell, lease, transfer, modify, adapt, translate, reverse engineer, prepare derivative works of, decompile, or disassemble the software provided. All rights reserved.

iancanada.mail@gmail.com

2023-08-30

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