Sorry its taken so long to post an update. I’m very busy at the moment with my PhD and I’m about to move house again.
Although I do have a couple of updates to post, I simply don’t have the time to write any detailed posts, but heres an outline of things to come:
I’ve decided to scrap the current word clock circuit. The I²C communications to the real time clock (RTC) only seem to work provided I don’t add any other functions to the microcontroller and I have a feeling that when it comes to getting the master/slave protocol to work with the other microcontroller, I’ll have even more trouble. I’ve decided to redesign the circuit, based around 64 pin surface mount PIC with a built in RTC. This will vastly simplify the design, although it does mean learning surface mount soldering.
In addition, I’ve got all the parts for my CNC z-axis (stepper motors, linear bearings etc), I just have to build it. I’ve also designed and built the stepper motor driver. I just need to find time to test this and blog about it. I’ll try and post a video of the motors moving when its done.
I’ve not forgotten about this blog, or my projects, I just need a few spare days to catch up on my to do list.
I’ve updated my bench power supply project description with a summary of the project (as follows):
This project started as me trying to fulfil a need for a reliable and convenient power supply and wanting to learn some lessons along the way. I designed the project in sketchup and then proceeded to go through various stages of construction. There were a few design changes along the way but nothing major. I decided to add an external voltage probe and a switch to allow voltage measurements either from the ammeter or ground.
You may have noticed that my previous post shows strange labels for the rotary switch. This is because i’ve changed the function of the rotary switch.
The ammeter causes a small voltage drop and so when the ammeter is being used as ground, the effective supply voltage is different to when the actual ground is being used. As such i’ve made the switch have the following options for the voltage measurement:
- Variable voltage to Ground (VG)
- Variable voltage to Ammeter (VA)
- External probe to Ground (EG)
- External probe to Ammeter (EA)
As such the previous schematic for the power supply needs updating. Below is the updated schematic:
I think this is a slightly more useful design as it allows me to compensate for the voltage drop across the ammeter. The only function i lose is the ability to measure the fixed outputs. But considering the external probe should be able to do this, i don’t really mind.
Note: There is an updated version of this schematic here
I’ve been unable to get to the tools lately to finish off the bench power supply case, so thought i would do an update for people looking to do a similar project.
I’ve drawn up the circuit schematic for the bench power supply. I’ve given colour coded labels for the cables coming from the ATX power supply (correct according to wikipedia at time of publication) and shown all the circuits that are needed, including all component values that I’ve so far decided on. The resistors attached to the LEDs will be chosen at later date, hence those have no values in this schematic.
I hope you find it useful
edit: I should add that i have some planned upgrades to this, such as relays to switch the binding post outputs based on the state of the power good line. This should protect any equipment from unstable voltages when the supply is first turned on. Also I would like to put resettable fuses in line with the outputs to prevent over loading any of the components. These are complications that can wait though. For now i just want to get the basics working.