Amplifier for Bluetooth speaker

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#62
Here are the resistor value changes to alter the gain I would probably drop it to 20dB...change R1 and R2 to 51k ohm resistors. Check what is there now just to be sure. Most of the ebaby/alibaba amps follow the datasheet for the TPA amps. Again assuming you have a TPA31XX amp...

Gain (SLV)
R1 = 51 kΩ, R2 = 51 kΩ 19 20 21 dB
R1 = 75 kΩ, R2 = 47 kΩ 25 26 27
R1 = 100 kΩ, R2 = 39 kΩ 31 32 33 dB
R1 = 100 kΩ, R2 = 16 kΩ 35 36 37
 
#63
A solution i was thinking about was to add a speaker banana plug to the back cover of the box to utilize with my charger so all i had to do was screw in the charger terminals like speaker wire and no fuss...just never got around to id.
 
#64
cjkpkg said:
Here are the resistor value changes to alter the gain I would probably drop it to 20dB...change R1 and R2 to 51k ohm resistors. Check what is there now just to be sure. Most of the ebaby/alibaba amps follow the datasheet for the TPA amps. Again assuming you have a TPA31XX amp...

Gain (SLV)
R1 = 51 kΩ, R2 = 51 kΩ 19 20 21 dB
R1 = 75 kΩ, R2 = 47 kΩ 25 26 27
R1 = 100 kΩ, R2 = 39 kΩ 31 32 33 dB
R1 = 100 kΩ, R2 = 16 kΩ 35 36 37
Click to expand...

Yes, like I show in the photo, I have 32dB gain with 100k + 39k. I can’t solder and don’t have smd resistors. Is there any over option I have?
 
#65
You have 3 options:
1. get a soldering iron and learn how to solder - its pretty easy, you can get SMD resistors lots of places online
2. install a volume pot in between your inputs and the amp board - will still require soldering
3. buy a new amp board with a volume pot already integrated.
 
#69
eX Radikal said:
Well, I've bought the BT module but I'm not very happy with it so I'll order the one that is on my Picture. That module has a DC-DC isolator like the one you refer in the back.
Here's the link.
Click to expand...


You didn't like the one that allows DIY friends without pressure?

I want to add BlueTooth inside a hifi amp, to use a phone as the only source. I have a spare 18Vac winding for power. So this looked good as it accepts 30v.



I notice it also has a 3.7-5v power input. Would I need two supplies, or is it a choice?


Did it simply work. I just want one that's controlled by the phone. No buttons. Just use the phone to find it and pair. Then send it music and it puts it out at something like RCA level.
 
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#70
friendly1uk said:
You didn't like the one that allows DIY friends without pressure?
Click to expand...

Ahahah, I like it but it has a little problem with the some buttons (or so I think), also is more complicated to program than the other I'll buy that have the pins right in the PCB.
I'll use it probably in other project when needed 🙂

friendly1uk said:
I want to add BlueTooth inside a hifi amp, to use a phone as the only source. I have a spare 18Vac winding for power. So this looked good as it accepts 30v.

I notice it also has a 3.7-5v power input. Would I need two supplies, or is it a choice?

Did it simply work. I just want one thhat's controlled by the phone. No buttons. Just use the phone to find it and pair. Then send it music and it puts it out at something like RCA level.
Click to expand...
It probably works with only one PS but need to get an isolator so you don't get digital noise.

Another thing, for example, with my iPhone I can fully control my xiaomi speaker but some androids can't control volume, for example. It's probably programmable in some BT modules, I dont know.
If you want something very simple, you can "steal" my idea, capacitive touch buttons and hide it under top cover of your case. 🙂
 
#71
The friends one had buttons to push? I thought it said no pressure 🙂


I cheaped out spectacularly. $2 lol 3.7-5V MP3 Bluetooth Lossless Decoder Board Car Stero Speaker Amplifier Module | eBay

I think it's meant to drive a speaker really, but my amp will have a high impedance input. I will use a divider to get down to rca levels.
Edit: It's not going to like my psu, but I have old phone chargers piling up that can provide that 5v.



My appetites been awakened now. I'm still looking for something better. Or known.



I've been back n forth, but don't see anything about buttons. I don't want any to be honest. I know my android volume works on the cars BlueTooth connection, and this project is actually for a friend with iphone. Fingers crossed it works, but I'm still looking for better ideas.
 
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#72
It doesn't have buttons to push, but the connnectors are there 😛
Anyway, I got almost all my money from the BT module.
The reason I want a CSR chip is because it can be programmable and configured with built in DSP.

Well, you need at least one button to turn it on/off, right?
Good luck with your project 🙂
 
#75
#76
I don't think you can fast charge from usb. The C rating of 4 in parallel should be quite high.



As you're talking 3.7v, I will presume li-po. As found in many phones. I have seen these charged with phone chargers. Even many cells is series, from many phone chargers. The risk is, I have never seen a phone charger, that was a phone charger. They have just been a psu.



I keep an imax b6 as a spare charger. It will charge a single cell (or parallel string) and looks after the cc/cv charging. Basically deciding the constant current level, and when to switch over to constant voltage and reduce the current at the appropriate rate for your battery chemistry. Stopping the charge when it's done. The bms doesn't do this. They have no voltage or current regulation, and at 1s no balancing. Just high and low level cut-out and some sort of fuse like behaviour for high discharge rates and short circuits.



So perhaps a bms from your links is fine, but you still need a charger. Not a power supply.





Hobbyking might be a good source for a bms, but beware any advice that RC owners give regarding charging. Same on the electric bike forums. Many progress from toys to bikes, and think the same charging rules apply. Tell newcomers it's the way, and then a house burns down. Every couple of years like clockwork.





Some 18650 cells aimed at e-cigs are classed as protected cells. There is a bms of sorts inside them. You can't flatten them, and desktop chargers exist. So they are about as complicated to use as an old ni-cad.



My pound store was selling small battery packs intended as phone chargers. They both charged and supplied power via usb sockets. Inside was an 18650. So there we have a very cheap 18650 charger and bms circuit. They often smoke, but the circuit could be worth a look at.
 
#77
I'm gonna use 18650 batteries (Samsung INR18650-29E) with this (powerbank) module to control charge of the batteries: 3.7V to 5V 9V 12V Lithium Li-ion 18650 Battery Boost Charging Board Type-C QC3.0 699958498986 | eBay

I've read the datasheet of the controller IC present in this module and seems very good with correct charging mode of the cells.
This way I have a really nice control of the charging of the batteries while the added function of having a complete QC3.0 powerbank.

For the Step-Up module, I've won this one (couldn't find anything better than 3V+ input with a current of 5A): 5A DC-DC Boost Step up Power Module Voltage Converter 3v~35v to 5v 6v 9v 12v 24v | eBay

For the BMS I found 2 modules but can't choose which one I'll buy (please check 2 posts above). Can someone helps me to decide?

Thank you
 
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#78
I might be losing my way a little.
The charging board will just be for charging.
The boost board will be for discharging.
The bms your looking for is just to stop the cell dropping below ~3v while discharging through the boost board.





I'm quite sure Hobbyking do a battery saver type thing, with an alarm as you approach cut-off. Model planes use them, as a very light weight option. Just to protect the cells from damage.



Maybe? 5A Round PCB Protection Circuit Board for 18650 3.7V Li-ion lithium Battery Cell | eBay
 
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