Help with building your Speeduino, installing it, getting it to run etc.
By JohnB
#60719
Hello, my name is John and i'm new to speeduino and arduino-microcontrollers in general although i'm quite experienced in electronics and mostly power supplies.

I have recently started building a Speeduino v0.4.3c PCB as per the official BOM and it is now complete.

I have a question since i'm testing the integrity of the board before i proceed with the Arduino so to not cause any damage.

I connected the board to stable +12v using a battery, everything looks okay, nothing shorted, the board shows 10mA idle current consumption, nothing gets hot aswell.

I'm getting a perfect +5v from the regulator output which is also present on the 4424 ICs when IGN jumper set to 5v.

The problem is the +5v above the pins 20 and under Gnd on the left down corner only show +2.5v between +5v and ground.

I had installed a diode array consisted of 1N5819 schottky diodes instead of SP721APP, i thought this could be the problem but once i desoldered them i keep reading +2.5v on the pin 5 of the dip-8 on the board.

I traced the PCB and the 2.5v goes to R7 which has 2.5v on it's left and +12v on it's right, aswell as to the pin going to Pin 4 - Digital of the Arduino, making me think there's no immediate connection to +5v from the regulator there.

Is the so called "proto" zone powered solely by the arduino?

Isn't it supposed that the board will pass +5v from the regulator to those pins?

Or is the arduino somehow powering those pins which does not since it's not connected?

If those are powered by the Arduino, is it normal to find +2.5v there?

Sorry for the dumb question, i have absolutely ZERO knowledge to digital electronics.

I'm trying to be sure about the board before i proceed connecting the Arduino and possibly cause damage.

Thanks.
User avatar
By PSIG
#60736
Don't bite too deep yet. First, I don't know what your location:
JohnB wrote: Sat Jan 21, 2023 11:49 am The problem is the +5v above the pins 20 and under Gnd on the left down corner only show +2.5v between +5v and ground.
means for sure. Please post a photo designating the pins tested, or post an edited version of the PCB image, or something else for clarity.

You can see on the v0.4.3 schematic, that R7 feeds the Battery Reference Voltage on Mega pin A4. If that circuit is involved there is an error, but let's be sure we're identifying the same points first. If someone else is interpreting your info better than me, they will jump in here. 8-)
By JohnB
#60738
Hello, thanks for your reply.

Upon checking the schematic in higher depth i realized R7 and R21 on the Battery Reference Voltage circuit should act as a voltage divider if we try to measure voltage there, so i verify it is normal to find 2.5v between R7-R21 and ground as that is what occurs from the equation.

Till here we're good.

I uploaded the schematic with the places i find 2.5v being circled black.

The purple colored circle from what i understand is where Arduino should power that place of the circuit with +5v, so this section isn't powered by the regulator.

Since there is no Arduino connected i would assume the 2.5v leakage i measure where 5v should be present by the Arduino is due to R8, and even though there shouldn't be anything there, it appears that it's a feature of the design that is allowing it.

I'll appreciate it if we can verify this, i'm trying to be sure i will not blow up a genuine Arduino board. 😂

Like i said, electronics wise i understand quite everything, Arduino wise i know nothing.
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By dazq
#60739
Please be aware that the Arduino does NOT power anything from its onboard regulator . The main 5v regulator on the speedy PCB powers any part of the circuit needing +5v including the Arduino itself.
By JohnB
#60740
It sure has no ability to power anything from its own board, but does it redirect +5v sourced from the regulator to the pin i've circled purple when powered on? If so, +5v power would be present to those pins i'm talking about when Arduino would be present(?).
If not, that is the problem, i'm getting 2.5v out of those without an Arduino on it.

If there's anyone with an assembled v0.4.3c willing to power it on and check the voltage to those pins without an Arduino present, it would be a highly appreciated act.
By LPG2CV
#60741
I think those areas of concern should have 5v from 12v supply. I suspect is so the mega can be supplied from usb.

Common errors, are diodes around the wrong way. There are some caps on the power supply that are directional as well.
User avatar
By PSIG
#60746
dazq wrote: Sun Jan 22, 2023 11:52 am Please be aware that the Arduino does NOT power anything from its onboard regulator . The main 5v regulator on the speedy PCB powers any part of the circuit needing +5v including the Arduino itself.
JohnB wrote: Sun Jan 22, 2023 12:15 pm It sure has no ability to power anything from its own board, but does it redirect +5v sourced from the regulator to the pin i've circled purple when powered on?
To confirm, the Mega receives 5V from the Speeduino board regulator on the Mega VIN pin -or- the USB jack, and passes it through, bypassing its own regulator, to some 5V areas through the 5V pin. The Mega does not use its on-board regulator, but the Mega is part of the completed circuit.

If you are reading 5V on the Mega VIN pin location, the PCB regulator or USB power feed is functioning. That does not mean everything is correct, just that part.
JohnB wrote: Sun Jan 22, 2023 11:01 amSince there is no Arduino connected
JohnB wrote: Sun Jan 22, 2023 12:15 pmIf so, +5v power would be present to those pins i'm talking about when Arduino would be present(?).
Yes. This is important, as back-feed and division of voltages on an incomplete board can be confusing. Also note your Mega circled pins are 5V and A3, not A4 — if that changes the discussion.
By JohnB
#60752
Thank you both for your replies.

I've checked the components on the PCB including the 5v lines but everything appears to be alright and soldered well, so i guess it is as it should.

As for the pins, i've made a mistake on the schematic, it's the A4 pin that has 2.5v, the A3 doesn't seem to have any activity, it appears to be grounding through C18 so that makes sense.

Tomorrow i'll get some schottky diodes to recreate an SP721APP alternative on a perf board and we'll see what would come into play with the Mega connected. I messed up the previous diodes when i desoldered them for further testing, they were directly soldered on each other assembling an ugly mess. :lol:

I'll give you an update when i'll have one, i hope everything turns out okay, i'm very excited for this project.
By JohnB
#61077
Hello.

Just to give you an update with the matter, i proceeded completing the Speeduino and it appears that the 5v lines have 5v on them with the Arduino connected to the board and everything seem to work fine so far, i even connected an HC-06 Bluetooth on the 5v proto output.

So if anyone is wondering and had the same issue, without the Arduino on Speeduino it is normal to find 2.5v there as there is no direct connection of the regulator to those parts of the board, but once Arduino is connected everything is up and running at 5 volts.

Thanks everyone for your input.

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