Generic Battery + Arduino = Happy Solo

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thanks for chopping:))) chop chop. i like this english word. it remind me of something. chop chop chop.
LM4040 is 1% accuracy. you don't want to use additional voltage reference ic? then it need to pull one pin header from vcc of regulator. let me know.
one single 0805 led consume about 20-25ma. so 160-200ma.
I checked pins out and allocate them as follow.

led1 -> D6, led2 -> D7, led3 -> D8, led4 -> D1, led5 -> D2, led6 -> D3, led7 -> D4, led8 -> D5

then 4 pins(D4,D3,A7,D13) are still available. but one of them(D13) is allocated to builtin led as we know. if you give up builtin led. it is possible to put 4 bits dip switch within board. if not, 3 bits. and pull down is easier to wiring than pull up in this case. need to change code.

about pcb manufacturing, 2 oz is usually 2-3 times more expensive than 1oz. also they have same pricing policy for size out of 100x100mm. so i will try to stay with 1oz and smaller than 100mm.
You could cut down the LED's from 8 to 6. I only used 8 as that was the neopixel board i had. This would save some space and pins.

Have you used D9 for the Neopixel? A 3 DIP switch (or 5 if you dropped a couple of LEDs) would still be useful and leave D13 for the I2C flickering (showing coms working etc). If you turn on the internal pull up resistors in code then the DIP switches only need to be connected to the inputs and ground and no other resistors are needed.

Since the Pro Mini doesn't have an exposed vref then the 5V regulator is all that is needed to power the board and will supply its own reference voltage. I would still use a 1A or higher voltage regulator to make sure its not operating near its max rating.

Even if the 2oz board is twice the price it will make it easier to allow the required current to flow and help get the size of the board down with track size. In the scheme of things this will be a small one-off cost and allow a bit of a safety margin.
 
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I haven't been able to find my Pro Mini board so I will have to wait until the ones i ordered arrive and can then test it with my Solo's.
 
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You could cut down the LED's from 8 to 6. I only used 8 as that was the neopixel board i had. This would save some space and pins.

Have you used D9 for the Neopixel? A 3 DIP switch (or 5 if you dropped a couple of LEDs) would still be useful and leave D13 for the I2C flickering (showing coms working etc). If you turn on the internal pull up resistors in code then the DIP switches only need to be connected to the inputs and ground and no other resistors are needed.

Since the Pro Mini doesn't have an exposed vref then the 5V regulator is all that is needed to power the board and will supply its own reference voltage. I would still use a 1A or higher voltage regulator to make sure its not operating near its max rating.

Even if the 2oz board is twice the price it will make it easier to allow the required current to flow and help get the size of the board down with track size. In the scheme of things this will be a small one-off cost and allow a bit of a safety margin.
little bit confused. when arduino is starting, aref is vcc(from regulator). no need to do anything if you want to use vcc as vref. but you inserted 'analogReference(EXTERNAL)' in your code. it does mean you are connecting external reference voltage to aref pin. i thought you temporarily connected vcc to vref and change it later. anyway i understand you don't want to use external one. practically it is not any matter. you can leave it blank even if board is designed to have external one.
D9 will be for neopixel. D13 won't be used. regulator will be 1117 with 22uF tant-capacitor. I will consider your offer of removing one or two leds and give spare pins to 4 bits dip switch with internal pull up.
regarding pcb size, 100x40mm is in my mind. may be ok with 1oz. will see.
 
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little bit confused. when arduino is starting, aref is vcc(from regulator). no need to do anything if you want to use vcc as vref. but you inserted 'analogReference(EXTERNAL)' in your code. it does mean you are connecting external reference voltage to aref pin. i thought you temporarily connected vcc to vref and change it later. anyway i understand you don't want to use external one. practically it is not any matter. you can leave it blank even if board is designed to have external one.
D9 will be for neopixel. D13 won't be used. regulator will be 1117 with 22uF tant-capacitor. I will consider your offer of removing one or two leds and give spare pins to 4 bits dip switch with internal pull up.
regarding pcb size, 100x40mm is in my mind. may be ok with 1oz. will see.
When i started i was looking to use an arduino nano as it had the usb port for debugging etc. This one had the vref pin exposed so you could provide your own reference voltage and it would use that for the analogue read commands. The Pro Mini board doesn't have this so the analogReference(EXTERNAL) command is not needed and the vref voltage will come internally from the pro mini. In the V3 of the code i have commented this out.

Now just to confuse design matters further......

If you have the arduino at 90 deg (to reduce the board height) the nano is the same height and only 10mm longer, it give easier access to the A4 & A5 pins for I2C and allows for a controlled vref. Then there is also the USB for easier programming.....

1567621583606.png
 
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I decided to solder MCU(atmega328) directly to the board. It make everything simple and clear. also it is actually nearer to final destination.

pcb_top_bottom.jpg

dimension.png

- prepared small jumper pad to open/close D10 to led/dip switch. default is open to led. cut jumper trace and solder the other make D10 open to dip switch.

- 8 pcs of single led is 020 SIDE led. not 0805 or 0603 led. refer to BOM.

- 8 leds are connected to D12 - D5.(from right to left on the bottom)

- dip switch is connected to D3,D4,A7,(D10) as a way of internal pull up.

- D9 is supposed to drive Neopixel(or similar digital led strip).

- one i2c connector is prepared.(no pull up resistor)

- one usb/ttl connector is supplied to program atmega328.

- have no idea where to buy solo bat female connector. simplest way is to break solo battery to get it from.


Since arducopter are supporting solo from battery monitor. you can use this board for not only solo but also any with arducopter/4S lipo. i'm planning to add xt60 female connector substitute to solo's one.


<Warning>
1. schematic is very simple but board is little bit picky because of high current. trace width for positive current are designed to endure more than 20A(even for 1oz) but need to strengthen negative one to make thing sure.(especially for 1oz copper pcb) just solder trace or simply connect two point with 14 awg cable.
high_current_soldering.jpg


2. board have never been tested. you can use it but it's at your own risk.

3. traces exposed to air(no mask) is much better to radiate heat. and it is needed for high current. but if you feel uncomfortable. you can use two 2.5mm screw hole to cover board with some 3d printed plate/housing or any other.
 

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I decided to solder MCU(atmega328) directly to the board. It make everything simple and clear. also it is actually nearer to final destination.

View attachment 10450

View attachment 10451

- prepared small jumper pad to open/close D10 to led/dip switch. default is open to led. cut jumper trace and solder the other make D10 open to dip switch.

- 8 pcs of single led is 020 SIDE led. not 0805 or 0603 led. refer to BOM.

- 8 leds are connected to D12 - D5.(from right to left on the bottom)

- dip switch is connected to D3,D4,A7,(D10) as a way of internal pull up.

- D9 is supposed to drive Neopixel(or similar digital led strip).

- one i2c connector is prepared.(no pull up resistor)

- one usb/ttl connector is supplied to program atmega328.

- have no idea where to buy solo bat female connector. simplest way is to break solo battery to get it from.


Since arducopter are supporting solo from battery monitor. you can use this board for not only solo but also any with arducopter/4S lipo. i'm planning to add xt60 female connector substitute to solo's one.


<Warning>
1. schematic is very simple but board is little bit picky because of high current. trace width for positive current are designed to endure more than 20A(even for 1oz) but need to strengthen negative one to make thing sure.(especially for 1oz copper pcb) just solder trace or simply connect two point with 14 awg cable.
View attachment 10457


2. board have never been tested. you can use it but it's at your own risk.

3. traces exposed to air(no mask) is much better to radiate heat. and it is needed for high current. but if you feel uncomfortable. you can use two 2.5mm screw hole to cover board with some 3d printed plate/housing or any other.
This is great work. How are we supposed to program the MCU?
 
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I decided to solder MCU(atmega328) directly to the board. It make everything simple and clear. also it is actually nearer to final destination.
Another awesome job..... Great idea to add the chip to the board, this was the ultimate plan (may posts back) but i had but just didn't have the know how to do this. Do you have the eagle file to look at your circuit? Did you look at getting the board assembled or have you just ordered all the parts (other than the Solo plug - i know there was talk Molex would do a run for a 1,000. Maybe we could group fund this will still happen and people are interested).

My arduino boards should arrive tomorrow or Wednesday so i will hopefully be able to test them by the end of the week. I know this won't help this design of the board....
 
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This is great work. How are we supposed to program the MCU?
Sorry. I forgot to mention about it.
expected problem is bootloader. if you buy a atmega328p mcu. it should be fresh one which you need to burn bootloader yourself. for this, you need usb programmer connect to SPI pins of mcu. after, you can download program through usb/ttl as you are doing now with arduino. but i didn't open SPI pins out on the board as you saw cause this is only one time job and you need to buy extra usb programmer. so here is solution.
buy atmega328p which already have bootloader for arduino ide. or take mcu out of arduino board with heat gun. it is not difficult as you think. just don't forget to heat bottom side of board. mcu won't be damaged at all. don't use your bare hands but some tool like tweezers. besides a price of atmega328 mcu is sometimes more expensive than arduino pro mini. well...

soldering mcu is usually not a piece of cake job for hobbyist like us. but if it is 'atmega328p-au', you could peacefully play with it at one of quiet sleepy night. in compare with other monsters.
 
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Another awesome job..... Great idea to add the chip to the board, this was the ultimate plan (may posts back) but i had but just didn't have the know how to do this. Do you have the eagle file to look at your circuit? Did you look at getting the board assembled or have you just ordered all the parts (other than the Solo plug - i know there was talk Molex would do a run for a 1,000. Maybe we could group fund this will still happen and people are interested).

My arduino boards should arrive tomorrow or Wednesday so i will hopefully be able to test them by the end of the week. I know this won't help this design of the board....
what you need is just buy all parts which are in BOM and also order pcb from manufacturer like JLCPCB or any other. eagle file is not well organized. i am afraid to upload. i will upload in a week. it shouldn't be late because it take time to receive parts and pcb. but actually gerber file have everything what you need.
i ordered parts and pcb yesterday. but they, china will be in the time of holyday this week. it will take longer than ever. hopefully one and half or two week??
1,000 is quite quantity. if such a number want to buy. also crowd funding should be easily possible. i know chinese company who are manufacturing(assembling) various boards.
 
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If there is any way to break out some pins or pads to allow usb re-programming it would increase the usefulness and future proofing of this board
 

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