Lab supply progress - Rectifier board redesign

I've finally made some progress with the power supply. After re-spinning a board and twice setting my diodes on fire, I now have a working first stage.

In the video below I give you a quick run through of my work and also show the inrush current limiting board and the regulator stage.

As I've mentioned before, this power supply will also be modular, but not only in the sense that each stage will be a separate board, but even at the board level parts are optional. This allows for you to build a bare bones analogue PSU through to a fully connected lab grade power supply.

Leave comments below. :-)

CremaBot: PCB assembled

The PCB's finally arrived from OSHPark.com and I have to say that I am very impressed. If only it wasn't for the South African Post Office being so slow, this would be a fantastic option every time.

 

The board below was as I took it out of the packaging. You can still see the tabs attached where they came off the panel.

Here is the board again with most of the parts, but communica.co.za where I buy most of my parts had the opto-couplers and the 74595 on back order. They also ended up giving me the through hole parts for the voltage regulators instead of SMD's.

Below is the board after soldering, but before I removed the solder flux residue. You can also see the missing 5 volt regulator.

This board is loaded on both sides. Below you can see the bottom side with the 12 volt regulator fitted in place.

And here is the final product, cleaned and with the Arduino Nano fitted. Only thing left to do is to make up the cables and we should be ready to test and finalise the software.

The board is still missing the 5 volt regulator, but should operate happily from the USB power in the first phase until we install the stepper motor driver, at which point we will have to supply external 12 volt power.

Optical End-Stops

posted 2 May 2014 09:13 by David Taylor   [ updated 3 May 2014 06:55 ]

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When I looked at an Optical End-Stop for the first time, I noticed it had 4 pins while most diagrams show it with 3 pins. I then took one of my Optical End-Stops apart and looked inside to see how the device is wired up. In my case I could do this non-destructively, and I could close it back up. Internally the device has a small PCB which has two of the pins connected together.   I looked around for an interface circuit to make my optical End-Stops work on my 3-pin Ramps 1.4 board and found the hand-drawn diagram below by RetireeJay on the Printerbot Talk forum on the same subject.   I figured I could get rid of at least one resister and came up with the circuit below, which works just fine. I had some Vera board lying around and made up the board as follows. which ended up being about 1.5cm x 1.5cm. Here is a photo of the final product. On this circuit the LED turns off when the optical end-stop is triggered and the LED's aren't super bright, but it does the job by passing about 2.3mA through the LED when it is tuned on.