I’m still waiting for that replacement LCD to arrive from china, i’ve ordered another from a UK seller.
I’ve not been sitting around twiddling my thumbs though; a while ago i saw a schematic for a stepper motor driver on instructables. It seemed a little over complicated to me and i figured i could easily build one using one of the PIC microcontrollers that i have, so i set about designing a cheap 3 channel stepper driver using just a 40 pin PIC and some mosfets. The advantage here is that i can give it a number of interface options such as a parallel interface, an RS232 interface or an I²C interface. There may also be options to include an LCD for status display.
The stepper driver circuit had reminded me of another one of my projects and i got the itch to start it. This is my CNC project. Its an MDF construction and the plan is that it will eventually be able to build a better version of itself. I’ve already started construction so I should soon be posting my designs.
- My Adjustable Voltage Circuit
- My Panel Meter Circuit
- My Aluminium Supply Case (Labelled)
- 2x DPDT switch
- Green Binding Post
- 4x Red Binding Post
- 4x Black Binding Post
- 3mm Red LED
- 6x 3mm Green LED
- 7x 3mm LED panel clips
- 4P2T rotary switch
- Amp Panel Meter
- Voltage Panel Meter
- Red Multimeter Lead
- 2x 6mm knobs
- ~20cm of 3mm 3:1 Heatshrink
- 2x TO-220 heasinks
- ~50 Crimp terminals
- Lead Free Solder
- 3x 47 KΩ resistors
- 3x 5.6 KΩ resistors
- 3.9 KΩ resistor
- 820 Ω resistor
- 12 KΩ resistor
- 1.8 KΩ resistor
- Soldering Iron
- Crimping tool
- Snipe nosed pliers
- Wire cutters
- Glue Gun
- Phillips screwdriver
- 2mm Allen key
For most of this it should be clear how it goes together. The circuit construction just followed my power supply schematic. If there is anything that needs explaining further then feel free to ask. Unfortunately i got a bit carried away at some parts and forgot to take photos, I’m still learning to take my time.
The panel meters for my DIY bench top power supply have arrived from china. One is a 20v voltmeter and the other is a 5A ammeter. I ordered them from ebay and at a cost of around £6 each, they are far cheaper than anything available locally.
On unpacking the meters i found this rather interesting note:
It seems that the meters require fully isolated power supplies. It may be possible to power them from battery but then i have to mess about with relays switching them on and off and changing the batteries. Instead i hunted around and ordered some of these DC-DC modules. They are XP-Power IA1209S modules but any dc-dc module with between 9v and 12v isolated output will do. I chose these because they have a 12v input, 9v output and are cheap. They have dual outputs but this just means that they provide a -9v output as well as the 9v output. Obviously the -9v output isn’t needed.
Panel Meter Power Circuit
- 2 XP-Power IA1209S dc-dc modules
- Small piece of strip board (also called vero board)
- 6 lengths of multi-core wire (7/0.2mm core)
Only basic tools are required for this circuit. These should form part of any electronic engineers arsenal, as discussed here. I just used the breadboard as an extra step
When they arrived I tested them on breadboard first:
I’ve drawn up a nice schematic to show how simple the wiring is:
Remember to cut the tracks on the board between the two supply’s outputs if you’re using strip board.
This time I powered up the circuit using the jump starting trick i mentioned in my previous post and tested the output using a multimeter. The output read 10.5v but there was no load on them so this isn’t unusual. After wiring up one of the panel meters, the output voltage dropped to a more sensible 9.3v
Notice that i have a power resistor (large white block) to load the supply and ensure i get a nice consistent dc source. This is sitting between 5v and ground and is 10Ω. This gets quite hot so until i can give it a heatsink and some airflow, i’m only running the supply for short periods.
Next i soldered the dc-dc modules to some strip board in the layout shown in the schematic above. Remember to cut the tracks between all the outputs of the dc-dc modules, you want those outputs to be completely isolated.
The result is some nice blue:
You can see the circuit in the top right, just below the ATX cable connector. I used a salvaged piece of stripboard from my earlier mishap, hence the additional yellow wire to bridge previous cuts. The breadboard is just to help distribute power and to hold the power resistor.
My next step is making the aluminium box that all this will go into. After that it won’t be long until this project is complete