PCB #16

LigasN · 2022-05-02T14:49:42Z

LigasN
May 2, 2022
Maintainer

All parts, documentation, and stuff about the PCB project.

LigasN · 2022-05-02T14:49:58Z

LigasN
May 2, 2022
Maintainer Author

Light connector:
Degson - DG308-2.54-02P

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LigasN · 2022-05-08T15:40:29Z

LigasN
May 8, 2022
Maintainer Author

The voltage regulator for Raspberry supply needs to have parameters:

output current - 1.34 it is better for Raspberry to have 2,5A (producer said that)
input voltage - 3.7V * 4 batteries in series = 14.8V
output voltage - 5V or a little more like 5.2V

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LigasN May 8, 2022
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LigasN May 15, 2022
Maintainer Author

Resign from internally configured LM1085, because there is possible to set up 5.2V for Raspberry board supply and have light power control.

LigasN · 2022-05-11T22:29:56Z

LigasN May 11, 2022
Maintainer Author

This can be better: https://botland.com.pl/przelaczniki-dzwigienkowe/8392-przelacznik-dzwigniowy-on-off-kn3c-101-250v-6a-5904422311674.html

Then with connector: https://botland.com.pl/zlacza-ark/2554-zlacze-ark-raster-35mm-2-pin-5szt-5904422353346.html

LigasN · 2022-05-09T21:33:58Z

LigasN
May 9, 2022
Maintainer Author

Bipolar transistor to turn on/off 12V supply for lights:
CDIL Semiconductors BCW66G NPN 0,8A, 45V, 330mW
https://static1.squarespace.com/static/5416a926e4b09de8832655bc/t/5d42ad2b5cccc300011e8b63/1564650797776/BCW66F_G.PDF

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LigasN May 10, 2022
Maintainer Author

https://www.electricalelibrary.com/en/2018/07/02/how-to-polarize-the-bjt-transistor-part-1/

Ib = Ic(sat) / hfe
Rb = (Uin-Vbe)/Ib

Ic(sat) = 10mA, hfe = 110
Ib = 91uA -> Rb = (3.3 - 0.7) / 91u = 28571 Ohm

Ic(sat) = 30mA, hfe = 120
Ib = 250uA -> Rb = 2.6 / 250u = 10400

LigasN · 2022-05-11T19:34:26Z

LigasN
May 11, 2022
Maintainer Author

Capacitors:

tantalum: https://www.piekarz.pl/30602-kondensator-avx-10uf-16v/

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LigasN · 2022-05-11T22:03:43Z

LigasN
May 11, 2022
Maintainer Author

Soo, the next battery:
https://botland.com.pl/akumulatory-li-ion/9066-ogniwo-18650-xtar-2200mah-6952918341307.html
basket: https://botland.com.pl/koszyki-na-baterie/5240-koszyk-na-2-akumulatory-typu-18650-polaczenie-szeregowe-5904422374341.html

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LigasN · 2022-05-11T22:45:12Z

LigasN
May 11, 2022
Maintainer Author

Voltage stabilizer adjustable 3A: https://www.ti.com/lit/ds/symlink/lm1085.pdf?ts=1652640073874&ref_url=https%253A%252F%252Fwww.ti.com%252Fstore%252Fti%252Fen%252Fp%252Fproduct%252F%253Fp%253DLM1085IT-ADJ%252FNOPB%2526keyMatch%253DLM1085IT-ADJ

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LigasN May 12, 2022
Maintainer Author

Vout = 1.25V(1+(R2/R1))
Vout is adjustable by R2 so:

Vout min = 1.25V
Vout max > 4 * 3.7V
R2 > 1.2 kOhm

LigasN May 12, 2022
Maintainer Author

For raspberry 5.1V will be done by:
Vout = 1.25(1 + (R2/R1)), R2 = 330 + 39, R1 = 120
Vout = 5.09V

LigasN · 2022-05-12T16:12:52Z

LigasN
May 12, 2022
Maintainer Author

potentiometer: https://www.piekarz.pl/05977-potencjometr-rm065-rm-p2-5x5-202/

1 reply

LigasN May 15, 2022
Maintainer Author

The potentiometer is needed to make it possible to investigate light problems with weaker light sources as it is the prototype of the stand.

LigasN · 2022-05-12T21:47:31Z

LigasN
May 12, 2022
Maintainer Author

0 replies

LigasN · 2022-05-16T19:39:30Z

LigasN
May 16, 2022
Maintainer Author

6 replies

LigasN May 27, 2022
Maintainer Author

It works with a 47k resistor between input and output light source cables. It works because of the current divider rule (The first Kirchhoff rule).

LigasN May 27, 2022
Maintainer Author

The second problem was caused by two things. First, was ammeter connected right before raspberry (no idea why it is wrong but it causes rebooting). The second was too much difference between input and output voltage. I am measuring current now by connecting the ammeter after batteries. The second problem can be fixed by connecting the step-down voltage regulator for raspberry to two accumulators connected in series only. The second pair will be used only for light sources.

LigasN May 27, 2022
Maintainer Author

The step-down voltage regulator is heating anyway so there should be a radiator or sth attached to it.

LigasN May 30, 2022
Maintainer Author

One more thing is to connect the pin via a resistor to the ground, to ensure pin states.

LigasN Jun 2, 2022
Maintainer Author

Problem occurs to be not true. After replacing the transistor it works well.

LigasN · 2022-05-23T21:23:31Z

LigasN
May 23, 2022
Maintainer Author

0 replies

LigasN · 2022-06-08T16:49:16Z

LigasN
Jun 8, 2022
Maintainer Author

To-do list before printing PCB:

Calculate and check the pull-down resistor value
Add pull-down resistor to schematic
Change the Raspberry voltage regulator and buy
Test new DC/DC converter for Raspberry
Update schematic for the Raspberry supply
Update board project

0 replies

LigasN · 2022-06-09T10:59:06Z

LigasN
Jun 9, 2022
Maintainer Author

Raspberry supply voltage regulator: https://www.tme.eu/Document/949639eab2f7194baeac95dcad7e2dd3/AP1507x-DTE.pdf

6 replies

LigasN Jun 9, 2022
Maintainer Author

Raspberry supply voltage regulator in the shop: https://www.tme.eu/pl/details/ap1507-d5-13/regulatory-napiecia-uklady-dc-dc/diodes-incorporated/

LigasN Jun 9, 2022
Maintainer Author

Diode:
https://www.mouser.pl/datasheet/2/427/ssb43l-1767997.pdf
https://www.tme.eu/pl/en/details/ssb44-e3_52t/smd-schottky-diodes/vishay/

LigasN Jun 9, 2022
Maintainer Author

Calculations based on:
https://passive-components.eu/how-to-choose-the-right-inductor-for-dc-dc-buck-applications/?fbclid=IwAR3pjfMoje9W4Bx9vYtv5tKTdSNtyyKmopRzp0mcMnkpt9_t6x7gcEN-igE

https://www.analog.com/media/en/technical-documentation/data-sheets/ADP2302_2303.pdf?fbclid=IwAR0of-30OkK2Es2K5xtyRGCRMzyIjKZQX6vp88xYeUHGSZ0HtwGLhMZivGw

LigasN Jun 9, 2022
Maintainer Author

Inductor:
https://www.tme.eu/Document/0a0a45af3542fdef69db0e033325315b/HPI1040.pdf
https://www.tme.eu/pl/en/details/hpi1040-220/smd-power-inductors/ferrocore/

LigasN Jun 14, 2022
Maintainer Author

On input 2x 100n and 2x 4,7u all in parallel, on output 2x 22u in parallel as well.

2x 100nF
2x 4,7uF
2x 22u

LigasN · 2022-06-19T20:23:19Z

LigasN
Jun 19, 2022
Maintainer Author

The new power supply for Raspberry works fine. There is no heat problem. Below is an image of raspberry with the camera and LED turned on.

1 reply

LigasN Jun 25, 2022
Maintainer Author

For good output value 5.1 < Vout < 5.2, R1 was 7,27kOhm and R2 = 2,39kOhm

LigasN · 2022-06-22T22:19:15Z

LigasN
Jun 22, 2022
Maintainer Author

Pull-down resistor calculations

3 replies

LigasN Jun 22, 2022
Maintainer Author

Some stuff measured on the prototype board:

Ic - 67mA
The transistor needs at least Ib > Ic / Hfe(~200) = 335uA. Value is confirmed via simulation in the LTSpice project and on the PCB board.
Vbe = a little bit more than 0.7, like 0.76V

LigasN Jun 25, 2022
Maintainer Author

Calculations with electricalelibrary:
Ic(max) = (Vcc - Vce(sat))/Rc => Ic(max) = (12V - 0.3V) / 150Ohm = 11.7V / 150Ohm = 78mA (measured before min. 60mA - max. 67mA)

Ib min = Ic(sat) / hfe => Ib = 100mA (> 67mA to ensure correct work and its datasheet example value) / 200 (it was measured on PCB, should be around the correct value) = 500uA

Rb max = (Vin - Vbe) / Ib = (3.3V - 0.7V) / 0.5mA = 5200 Ohm, so I tested 4.3kOhm and I got 565uA.

LigasN Jun 25, 2022
Maintainer Author

For the pulldown resistor, I've checked that 10KOhm works just fine. From a couple of Internet sources, I have got to know that for raspberry powered by a battery it is even better to put a higher value resistor. So I decided to use 22kOhm. It makes 3.3V / 22kOhm = 15uA.

LigasN · 2022-07-08T15:09:40Z