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I have a circuit and a microcontroller. The circuit take 110 V AC, and I need 5 V DC to power the board. The circuit is plugged to a power outlet where it takes its power. What I need to do is to power the microcontroller from the wall plug. For that reason I need to convert 110 V AC to 5 V DC and since I am doing the PCB for the controller I though I can install the power supply on top of my board with a USB type power supply to power my board.

I wonder if there is existing schematics that I can use for that purpose? Ideally if there are ready to go Eagle files that can be used?

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  • \$\begingroup\$ Don't be lazy... I personally would rather design the schematic and create the design to learn. \$\endgroup\$ – 12Lappie Feb 16 '17 at 19:44
  • \$\begingroup\$ You are right, but to be honest I am a bit on the tight schedule, so if I can have plug and go solution I would prefer that. \$\endgroup\$ – ekuznets Feb 16 '17 at 19:51
  • \$\begingroup\$ Look up AC to DC power supply 5V there are scads of them \$\endgroup\$ – Voltage Spike Feb 16 '17 at 19:52
  • \$\begingroup\$ Yes, you can most likely purchase a power supply module. They make sense if your volumes are low and you need a switch-mode power supply. Linear supplies with an isolation transformer, bridge rectifier, smoothing capacitors and voltage regulator are easy to design and build. Be careful, 120 V can kill. \$\endgroup\$ – skvery Feb 16 '17 at 19:52
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    \$\begingroup\$ You didn't provide current/power requirement but I don't think that you need more than 1A. So, you may go for a cell-phone charger. \$\endgroup\$ – Rohat Kılıç Feb 17 '17 at 8:44
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I feel that it would be much cheaper (and safer) to use an already made 120v to 5v usb adapter that comes with most phones. A lot of them cost less than $2 and come in a rather small, sealed plastic casing, which would be hard to do if it was homemade. If you need to, you could solder wires onto the ends and use some heatshrink tubing to cover the plugs and use it that way rather than plugging it into a wall (like if you want to have it inside a lamp or stereo or whatever).

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Being in a hurry and getting designed something on a kind of uncharted territory doesn't really fit together.

If you are interested and want to research a bit yourself, I would go for the following solution. It's a slightly modification of "Das InterNetzteil- und Konverter-Handbuch von Dipl.-Ing Jörg Rehrmann".

Sorry, not enough points to give you the original resource - such a shame!

I have a LT-Spice schematic ready and provide you the images since I have no idea how to attach files here.

I'd like to give you some hints:

  • recommended rectification diodes (D1, D4, D5, D6) from original author: BA159
  • input voltage is 155V peak, so it calculates to approx. 110V rms
  • R3 and D7 should have a power dissipation of at least 3 watts
  • D7 could be replaced by a 5.1Vz type to get a voltage out closer to 5V DC
  • M1 shall be a power type of >=5A drain current and >=250V Vds. The one used here is just for simulation demonstration. A proper type is suggested by the original author: IRF830
  • due to harmonics on the grid, the output current shall not exceed 20mA. Before you connect your controller PCB, do a total power consumption measurement on a regular 5V DC source.

schematic plot

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    \$\begingroup\$ What the pluck? Using 1N4148s for line voltage rectification? Are you serious? \$\endgroup\$ – WhatRoughBeast Feb 16 '17 at 23:38
  • \$\begingroup\$ you are right, sorry. Changed it, shall be something like 1N4005 or greater. Also removed the upper rectification branch, since it is only required for main loads \$\endgroup\$ – woodz Feb 16 '17 at 23:53
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    \$\begingroup\$ This is not a good circuit. Non-isolated. Low single digit percentage efficiency. Look at the simulation output, the 5V ripple is visible even at this scale. The ripple is probably in the 1V range. \$\endgroup\$ – rioraxe Feb 17 '17 at 2:44
  • \$\begingroup\$ added low pass filtering, even minimizes harmonics \$\endgroup\$ – woodz Feb 17 '17 at 7:54
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    \$\begingroup\$ The OPs question makes it clear they're not too experienced with electronics, and you recommend they rectify the mains. This is a bad suggestion. \$\endgroup\$ – Colin Feb 17 '17 at 8:24

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