Lab Power Supply: OpAmps, Analogue Control and Digital Monitoring

I've progressed to the point where I think the second stage of the Lab Power supply is probably ready for an initial board to be made.

In this video I go through the OpAmp design, the digital monitoring, Linear control and the design of the shunt resistors in the second of three main boards in the system.

Might be time to have at least the Raw Power board manufactured so that I can progress to a stage where I can start testing the design of the second stage.

CremaBot: Schematic Update

posted 23 Jun 2014 12:49 by David Taylor   [ updated 25 Jun 2014 22:48 ]

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While being in Cape Town on Business, I decided to make use of some free time and recorded a quick YouTube Video to provide an update on progress with CremaBot. Below is a Walkthrough of the Schematic: Since I recorded the video above, I've actually completed the PCB layout and ordered it from OSHPark. I've never used them before, so I'll let you know what I think of the quality and speed of delivery all the way to South Africa. More updates coming soon.

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.