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I'm starting my hobby electronics journey. I know how to read all the symbols and know how to solder. But I'm a bit confused with reading schematics that have multiple GND and the difference between VCC vs +5v.

Please take a look at this schematic. enter image description here

  1. Where do the ground points physical connect to?

  2. Do they symbolize the negative terminal on power source and therefore all GND points should connect to each other some how?

  3. There are VCC points and +5v points. Are they the same? If not, where do the wires connect to?

  4. Which power adapter can I use to power this station? THe schematics have +5v. If I got a laptop charger that was 19v 60watts 4amps, how would I use it to power the +5volts which is less than 19v of the charger?

  5. Also from one power adapter how would it get 15v ac and 9v ac power from?

I'm trying to replicate this soldering station. here.

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  • \$\begingroup\$ Try posting a schematic that isn't impossible to read/edit or you'll stay a penguin. \$\endgroup\$ – Andy aka Aug 9 '17 at 17:27
  • \$\begingroup\$ But I like the linked tool... \$\endgroup\$ – Eugene Sh. Aug 9 '17 at 17:27
  • \$\begingroup\$ You don't want to be a penguin forever. \$\endgroup\$ – Harry Svensson Aug 9 '17 at 17:29
  • \$\begingroup\$ @Andyaka, what don't you like about his schematic? It could stand to have more net labels, but it doesn't strike me as extraordinarily hard to read \$\endgroup\$ – fkoran Aug 9 '17 at 17:43
  • \$\begingroup\$ @Andy aka - its not my schematic. Its actually from the second link and shows 'Great Scott' as the author. If I was smart enough to come up with this, I probably would not have newbie questions \$\endgroup\$ – JuniorPenguin Aug 9 '17 at 17:46
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When you see ground or VCC connections they symbolize a common net. That is, it's a shorthand way to show all the pins that need to be connected to those rails without actually having to draw a ground or power wire on the schematic.

As you surmise, all the grounds, and +5Vs and Vccs, are indeed connected to their respective "together".

In this case Vcc is actually mislabelled, and badly so in my opinion.

Your Vcc shown on the schematic should actually be labeled as "RAW". It's simply the rectified and smoothed 9V AC voltage. The +5V signal is generated by the Arduido, and should more rightly be labelled Vcc.

Whether the arduino can actually supply enough current for all the things attached to that pin in unknown.

As for where to get 15V and 9V AC, you would need suitable transformers. If you want to use a laptop charger to get your RAW voltage, you would need to down regulate it to within range of the ARDUINO RAW input voltage range.

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  • \$\begingroup\$ Sigh..downvote and no comment.... Good work helping nobody. \$\endgroup\$ – Trevor_G Aug 9 '17 at 17:44
  • \$\begingroup\$ Sorry, forgot to Thank you Trevor. I actually up voted your answer but the system says I don't have enough reps to do anything. Can you clarify one thing? on the schematic, does the RAW + VCC and +5v connect on the same cirecuit or you are saying all the +5v connects together and all the VCC connects together but not with the +5v? \$\endgroup\$ – JuniorPenguin Aug 9 '17 at 17:52
  • \$\begingroup\$ @JuniorPenguin everything with the same name connects together. That is all the +5Vs and all the Vccs and all the ground symbols. The latter is just a visial aid to make it obvious. NOTE though... Vcc on the symbol is not the same as Vcc on the net. Hence my suggestion it's named wrong on the schematic. \$\endgroup\$ – Trevor_G Aug 9 '17 at 17:54
  • \$\begingroup\$ Hi Trevor, one more newbie question - you say that 9v ac and 15.5 ac need to be down regulated. In the tutorial link, it did have a transformer in bill of materials. Would that correlate to Q1 BTB26-600 and D1 2W10 + D2 2W10 modules? \$\endgroup\$ – JuniorPenguin Aug 9 '17 at 18:00
  • \$\begingroup\$ @JuniorPenguin down regulation would only be needed if you were replacing the 9V AC. You would still need an AC transformer for the 15V part using that circuit. \$\endgroup\$ – Trevor_G Aug 9 '17 at 18:08
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Treat every power and ground as an inductor and resistor with units of nH and mOhms and use XL(f) for switch transients and ground shift noise along with Ohms Law on load to Source.

Since a square area conductor has the same inductance for any size, a ground and power plane is obviously better than a track but sometimes a 100:1 L:d ratio is adequate.

Example when it is not adequate is like on 10: 1 probes with 100mm ground clips that resonate at 20MHz. You fat tracks for power and ground.

Keep in mind impedance ratio of source inductance and load capacitance and ESR of same for noise and avoid ground and power loops which act as antenna and also conductive noise. Use star or plane distributed grounds from power source and return for high currents. Nothing too high here, but the OLED display needs low analog noise for video signal to source. Add 0.01~0.1uF caps for insurance on each logic chip. I used an RLC Nomograph to avoid the mind numbing calculations of impedance to each component to understand frequency effects of parts and traces. Later for RF one uses stripline or microstrip calculators for f> 20MHz.

There are obvious basic suggestions, which you can read anywhere for Power ground , I just added some finer points, which may take you a while to grasp.

For example we often use Analog ground symbols separate than logic ground and Earth ground as each is simple a designated 0V reference for the signals using that. The same applies to 5V and Vcc. Each may be common or physically decoupled by understanding the charge and discharge current paths of high current logic pulses e.g. 10mA/10ns = 1A/us and large E-caps often have a limitation of 1~100us ESR*C time constant.

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  • \$\begingroup\$ Sir, your answer was very detailed and technical and also flew by my head. What training/articles/books/courses do I need to take to become a master Jedi like you? \$\endgroup\$ – JuniorPenguin Aug 9 '17 at 18:19
  • \$\begingroup\$ welcome to electronics.. the chip vendors have Application notes . If you read them all, then you can understand, but start with Ohms Law and Impedance for L,C(f) then apply KVL using these impedances \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Aug 9 '17 at 23:33
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Where do the ground points physical connect to? Do they symbolize the negative terminal on power source and therefore all GND points should connect to each other some how?

Yes, all the ground points should be connected together

There are VCC points and +5v points. Are they the same? If not, where do the wires connect to?

In this case VCC and +5V are not the same. Power enters the circuit from the 9V AC connector. D1 provides reverse polarity protection. After passing through D1, the unregulated, reverse-protected +9V voltage is called VCC.

VCC enters the RAW pin of the Arduino Pro Mini, where an on-board regulator converts it to +5V. That +5V then supplies the rest of the low-voltage components.

It's misleading that the schematic refers to the unregulated +9V net as VCC. It should be called RAW, V_IN, or +9V

Which power adapter can I use to power this station? Can I use a 19V charger?

The on-board regulator on the Pro Mini steps the +9V input down to +5V. You need to check the Pro Mini to see what it'll accept. Take a look at this page:

https://www.sparkfun.com/products/11113

Also from one power adapter how would it get 15v ac and 9v ac power from?

You'll need a multitap transformer.

It doesn't matter for the 9V input, but the 15V AC input needs to be AC for the triac (double triangle symbol) to operate, and it needs to supply enough current to run the soldering iron.

I'd suggest using a single tap transformer for the 15V input, and use any old 12V AC->DC power converter for the 9V input

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  • \$\begingroup\$ Thank you fkoran; your answer helped a lot along with Trevors. \$\endgroup\$ – JuniorPenguin Aug 9 '17 at 18:04

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