un1b0x - 2020 EUzebox BOM

Topics regarding the Uzebox hardware/AVCore/BaseBoard (i.e: PCB, resistors, connectors, part list, schematics, hardware issues, etc.) should go here.
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danboid
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Re: Unibox - WIP 2020 EUzebox BOM

Post by danboid » Fri Jul 17, 2020 4:47 pm

Yes, you're right! I'm not going to be replicating that thing! :D

As for the BOM, the most important thing is having a list of the 'exact' components. The source and price etc are secondary.

As I said in my first post, I know nothing about electronics. This is my first ever project so I've got some newbie questions for you.

I'm looking into wiring up the power circuit. I am presuming that the ground pin on the 7805 linear voltage regulator will be used as the ground? I'll have to buy a screw to screw the LVR into the breadboard. Would a certain material, type or size of screw be better for screwing into a breadboard or do I need to stick something between LVR and the breadboard before attaching it? Would you recommend placing some washers either side of the LVR screw hole?

Once the LVR is attached to the board, do I need to wire from the LVR ground pin to the ground pin on the power connector? I'd presume so but assume that I know nothing because that is the case. Nothing should be considered too obvious not to mention!

In this screenshot of the power schematic, I am presuming that the horizontal black lines I have circled in red mean 'wire this to ground'? That looks more like the battery symbol than the ground symbol to me so I'm not sure, being totally new to this. If it is ground, is it to the LVR ground or to the ground pin on the power connector or both?
Screenshot from 2020-07-17 15-56-13.png
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I'm not too sure about the +5 coming off the 10u/10v (or in my case, 10u 6.3v - do we think this will work? It does afterall say 9-12V on the schematic) does that mean that the positive terminal of the C5 capacitor is now the +5v 'source' (for the rest of the board)?

I have attached a photo of my 10uf 6.3V cap next to a 7805 for size comparison. These are apparently used on the normal UB but I'd have to order some 10uf 10v caps if you don't think I'll get away with using a 6.3V cap instead. I attached this pic because the cap looks significantly smaller to me than the C5 cap shown in Euzebox construction guide but then again it is just over half its voltage.
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The following pic shows how I currently intend to lay out the power components. I've not soldered any of these in place yet. Does this proposed layout look sensible enough?

I have deviated from the normal Euzebox layout in the positioning of the power connector because the board isn't wide enough to fit the power connector on the top edge. It is only just wide enough to fit the SD card adapter and the SCART connector next to one another.
IMG_20200717_161324-small.jpg
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Jubatian
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Re: Unibox - WIP 2020 EUzebox BOM

Post by Jubatian » Fri Jul 17, 2020 8:18 pm

danboid wrote:
Fri Jul 17, 2020 4:47 pm
I'm looking into wiring up the power circuit. I am presuming that the ground pin on the 7805 linear voltage regulator will be used as the ground? I'll have to buy a screw to screw the LVR into the breadboard. Would a certain material, type or size of screw be better for screwing into a breadboard or do I need to stick something between LVR and the breadboard before attaching it? Would you recommend placing some washers either side of the LVR screw hole?
You only need to use its ground pin, you can leave the top with the screw-hole unconnected. It is ground due to the internal design of the regulator, to be efficient dissipating heat it needs to be electrically connected, so it is rather informative (when you add heatsink, pay attention to not let it touching / shorting things, proper insulation). You don't need heatsink since the Uzebox doesn't draw such amounts of power (unless something is really botched up, it should only get a little warm during usage, not anything hot!).
danboid wrote:
Fri Jul 17, 2020 4:47 pm
I am presuming that the horizontal black lines I have circled in red mean 'wire this to ground'?
Yes, that's ground, so each of those circled in red are connected together. The "origin" is the negative terminal of the bridge rectifier (the B40C800 part).
danboid wrote:
Fri Jul 17, 2020 4:47 pm
I'm not too sure about the +5 coming off the 10u/10v (or in my case, 10u 6.3v - do we think this will work? It does afterall say 9-12V on the schematic) does that mean that the positive terminal of the C5 capacitor is now the +5v 'source' (for the rest of the board)?
Everything connected by wires are on the same potential. The actual source of your +5V is the regulator, the caps only help stabilizing that voltage.

(At very low level, it matters where you put individual components, particularly the 100nF caps and the 22pF caps of the crystal. The 100nF caps are important to be placed near the components they are associated with as they filter / stabilize voltage for them (and the wires themselves are also capacitors or antennas, picking up noise). The 22pF ones are important to be placed as close to the oscillator, and the entire stuff as close to the MCU as possible as at such small amounts, the capacitace of wires also matter!)

That cap should be all right since it is on the +5V side. If by some accident you had more than 6.3V there, the ATmega might also release its magic smoke...

Looks okay, if you connect everything all right. You could stand up that regulator to recover some valuable perfboard surface, like I mentioned, the heatsink doesn't need to be connected anywhere. Just let it stand upright.

If you have a voltmeter, keep measuring voltages as you progress. First solder on & connect the bridge rectifier, and check whether its +/- outputs are giving the proper results (between + and -, you should have the PSU's voltage). Then add the 470uF cap, check again. Pay attention to the polarity of these caps (the 100nF and the 22pF caps have no polarity requirement, however the 1uF and bigger, electrolyc caps, have, and if you mistake it, then fireworks :lol: ... Seriously, be careful, those will pop!)

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danboid
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Re: Unibox - WIP 2020 EUzebox BOM

Post by danboid » Sat Jul 18, 2020 6:47 pm

Thanks for that comprehensive response Jubatian! I'm pretty sure that answered all my questions and allows me to continue construction. You even pre-empted a question I should've asked but didn't regarding what components are sensitive over their placement. Big thanks!

There is one more component (that I'm aware of) that I don't quite have the exact part for. The Euzebox schematic for the SCART connector specifies a 3K resistor yet I currently only have 3.1K resistors, as these are used for the regular UB. Do you think I'll get away with using a 3.1K in place of the 3K?

I realised I didn't have any electrical tape and I very much suspect I'll be needing some solder wick (or in my case wire wool and flux) so I picked them up today and added them to the Tools section of the BOM which has been updated to 0.7 now.

EDIT

I've updated the tools section of the BOM again. Turned out the wire stripper I had bought isn't very useful for someone who wants to strip very short lengths of wire. Also, I can only strip one end with it. Poor choice.

I have wired the power connector to the bridge rectifier and tested that with the multimeter but I don't know if I can can bothered trying to do much more without a usable wire stripper as I'm having to use my fingernails and some wire clips and its very tedious to strip the wires like that.

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Jubatian
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Re: Unibox - WIP 2020 EUzebox BOM

Post by Jubatian » Sun Jul 19, 2020 2:56 pm

danboid wrote:
Sat Jul 18, 2020 6:47 pm
The Euzebox schematic for the SCART connector specifies a 3K resistor yet I currently only have 3.1K resistors, as these are used for the regular UB. Do you think I'll get away with using a 3.1K in place of the 3K?
It is okay, however the color reproduction will suffer slightly assuming the other resistors are 750 and 1.5K ohms. The 3.1K will weaken the lowest bit slightly of the R and G components.
danboid wrote:
Sat Jul 18, 2020 6:47 pm
I have wired the power connector to the bridge rectifier and tested that with the multimeter but I don't know if I can can bothered trying to do much more without a usable wire stripper as I'm having to use my fingernails and some wire clips and its very tedious to strip the wires like that.
Just use the excess leads of components for short wires! :D It is fine, they are sturdy wires, don't worry about that, after all, the components like the caps and stuff stand on those stubs on your board. And then no problem stripping! :P

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danboid
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Re: Unibox - WIP 2020 EUzebox BOM

Post by danboid » Sun Jul 19, 2020 9:42 pm

Thanks Jubatian!

If the colour is going to notably suffer then I will source the correct resistor.

I have now soldered in and wired up all or most of the power components. I was going to attach the crystal but I'm unsure if its polarity / orientation matters? If it does, how am I supposed to know which is leg 1 and which is leg 2 because it doesn't seem to tell you in the parts datasheet. I ask because the connectors seem to be labelled 1 and 2 on the schematic:
Screenshot from 2020-07-19 21-31-16.png
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Jubatian
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Re: Unibox - WIP 2020 EUzebox BOM

Post by Jubatian » Sun Jul 19, 2020 9:56 pm

danboid wrote:
Sun Jul 19, 2020 9:42 pm
I was going to attach the crystal but I'm unsure if its polarity / orientation matters?
No, it doesn't matter, so can go in either way! (Same for the 22pF and the 100nF caps, no polarity on those small capacitance ones as they are ceramic caps)

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danboid
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Re: Unibox - WIP 2020 EUzebox BOM

Post by danboid » Mon Jul 20, 2020 3:39 pm

Thanks Jubatian! I suspected as much.

I have ordered some 3K resistors, some 10uf 10V caps and updated the BOM spreadsheet to 0.9.

I'm hoping that is the last time I'll need to update it now until I have finished building it. When I am done I will revise the BOM and remove any components I bought but didn't use which should only be whatever parts the official UB BOM lists that the Euzebox doesn't need but maybe there'll be more?

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Artcfox
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Re: Unibox - WIP 2020 EUzebox BOM

Post by Artcfox » Mon Jul 20, 2020 7:37 pm

Another thing that you can do if you already have many 3.1K resistors in your possession (that have a high enough tolerance) is to just measure each one with a multimeter until you find one that measures 3.00K. It might take going through a bunch before you find one, but I've done that before when I was in a pinch. It doesn't scale well, but for a one-off, it might be an option.

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danboid
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Re: Unibox - WIP 2020 EUzebox BOM

Post by danboid » Wed Jul 22, 2020 1:21 am

Thanks Artcfox! That's a good suggestion but I've got some 3K resistors so I shouldn't need to do that now.

I need to wire up the 6-pin header now but I don't know which way round to do it. Unfortunately the Euzebox schematic doesn't show where the notch in the header is and the datasheet for the header was no use to me either as it doesn't seem to show 6 pins:

https://cdn.amphenol-icc.com/media/wysi ... /75869.pdf

How do I identify pin 1 on the 6 pin header?

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Re: Unibox - WIP 2020 EUzebox BOM

Post by Artcfox » Wed Jul 22, 2020 3:40 am

The datasheet is parametric and shows an example layout for N pins, scale N up and down as you wish.
It shows pos 01 and pos 02 on the left hand side:
Screenshot from 2020-07-21 22-28-03.png
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If you have the schematic, follow the VCC and GND traces back to the pins, and that should show you which way to orient it. Your programmer should fit one way into the socket, and the ribbon cable on the programmer should have a red line on one edge showing which side is VCC. Then trace the other pins on the socket back to the pins on the AVR chip and make sure they match up.

I grabbed this screenshot from the book I wrote:
icsp.png
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which I always refer back to when I need to make an adapter to connect my programmer to a board which uses a different layout of its ICSP pins (like the inline version on the Uzebox DTV).

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