ProtoDAC TDA1387 X8 project

[hifinet]

There is a chance of cell imbalance in a 2S series configuration during discharge, so it is best not to push them to a near discharge state without a balancer circuit. The voltage will drop rapidly below 6.0V for the 2S. When charged, the cells will rebalance.

A BMS will turn off the entire 2S battery when one of the cells reaches the low voltage threshold. I do plan to add the BMS, and see if there is an audible difference with the added resistance of the switching MOSFETs.

Some data: Freshly charged batteries at 3.52V Time 0: 6.95V with Kali/ProtoDAC. About 6 hours later it was still in the plateau region at 6.53V. Each cell 3.28V. 11 hours 6.41V (6.45V unloaded = 3.22V and 3.23V).

Note: I have previously run RPi2/Kali/ProtoDAC on 1200mAh LiPO with LT1963. Based entirely on a seat of the pants comparison with the LiPO, I don't think these 2.0Ah labeled LifePO4 have that actual capacity.


                                 Typical LifePO4 state of charge profile

[hifinet]

That is just for a PCB. No parts.

It doesn't need to be anything special. You might already have a suitable linear power supply (wall wart) in the 6VDC to 12VDC range. The old linear supplies weigh more than the SMPS, because of the larger transformer (you wouldn't want one thrown at you). In the US, it usually says "Class 2 transformer" on the label.  Current rating of 500mA for ProtoDAC alone is much more than required. Maybe you have an unused one around the house. This will get you the transformer, diodes and capacitor in one inexpensive unit.

Power supply requirement of ProtoDAC alone is 52mA (6.5mA X 8). 

Then add the LT1963 module with a cap on the input and the appropriate 10uF cap on the output. The regulator will make it very low noise. You can easily drop from 12V with little heat (0.364W).

[hifinet]

Yes. The LM317/337 board you ordered can take AC or DC input. It has the rectifier, caps and the regulators. I would not use a SMPS.

[varunach]

Hi @hifinet if I were to solder a green terminal block connector between the 5V and GND terminal what size connector should I get? 5mm spacing? I got my IanCanada parts today and about to start my project and wanted to solder a terminal block for the 5V supply wires from PurePi.

[hifinet]

Yes, 5mm green works. Be sure the polarity is labeled correctly.

[varunach]

Yes, 5mm green works. Be sure the polarity is labeled correctly.

@hifinet When you say polarity, red wire goes to 5V and black goes to GND right? Is that what you mean or does the terminal connector itself has any polarity indicator? Also do you know if any local stores sell the terminals or if i have to go the Amazon route (they only sell in bulk)?

[hifinet]

Yes, 5mm green works. Be sure the polarity is labeled correctly.

@hifinet When you say polarity, red wire goes to 5V and black goes to GND right? Is that what you mean or does the terminal connector itself has any polarity indicator? Also do you know if any local stores sell the terminals or if i have to go the Amazon route (they only sell in bulk)?

Correct. It's just when facing it from the RCA jacks, GND is on the left and 5V is on the right. It seems to be more common to find 5V on the left and GND on the right. The terminal does not have a polarity indicator. I recommend adding red paint or tape to the 5V terminal.

Here  There generally aren't any local electronics suppliers left, unless you live in a very large city.

[hifinet]

Since it's the weekend, I should mention that electronics parts can be found at local Amateur radio, AARL, antique radio meets and fests. The antique radios are also just fun to look at. Maybe you have one in your area.

[varunach]

Finally got my fifopi Q7ll installed. But I stumbled upon an issue. Once I turn on the power on the clean side, 3.3v, of the Q7ll I lose contact with moOde over WiFi. Once I turn it off again, moOde is back!!! Do I have to do something with the audio configuration to get it to connect to the Q7ll?

I’v really enjoyed all the latest discussions on power supply’s and caps. Regarding the Mundorf evo oil I really like them.

@OnkelPH How did you resolve this issue? I just got my IanCanada parts and I have the same issue. 

1. The RPi4 alone with Moode OS on a SD card boots just fine.
2. I installed the RPi4 on top of PurePi and connected the external power supply to Power Pi. I let PurePi charge for 2 hours. All lights lit up as expected. I was able to boot into the Moode OS and was able to access from my browser via Wifi. 
3. I turned the PurePi switch off. Installed the FifoPi Q7 on top of RPi4 GPIO (in other words connected to the dirty side 5V supply). I did not connect the 3.3V clean side supply to FifoPi Q7. Again I was able to boot into Moode OS via Wifi and able to access the interface from my browser. 
4. I turned the PurePi switch off again. Connected the 3.3V terminals from PurePi to FifoPiQ7's J5. And when i turned everything on, I was not able to boot into Moode and it seems to have gone into some sort of unresponsive state. Disconnecting 3.3V terminals from Q7 brings Moode access back. 

I tried all these steps with ProtoDac1387 driver and also with Generic I2S driver (that Ian recommended for Q7). Same issue.

Super frustrating   Any pointers would be appreciated.

CC: @hifinet @Tim Curtis for help as well

[hifinet]

What do the status LEDs indicate on the Raspberry Pi? Is there normal power and SD card activity?