Re: Electronic home switches made easy!
Well, I managed to get some of the switches assembled, the ones that DON'T require the kit. I have also sold a few, but, I have not heard a response from the buyers yet. I am sure they have not had a chance to place them on their machine yet. They did say that if they work as good as they look, it would be awesome!
Also, I got the boards ordered and they arrived two days ago. I spent yesterday assembling the parts. One part is super tiny, like a grain of sand. It's about a 0201 size SMD chip. It's one of the ESD TVS Diodes. I've added Electro-Static-Discharge protection to this kit to help protect the components. It won;t protect it completely, understandable, but, it will help greatly. most of the chips or 0603 size and smaller. Really tedious work to hand place them all. But the stencil I got for the solder paste works great! Makes it easier.
As you can see from the pictures, it is not completely assembled yet. I mis-ordered one part. I layed it out wrong on the circuit board using the wrong footprint size for the chip. Luckily, they make that identical chip in the size I laid it out for on the PCB. Got lucky there. Just waiting for it to arrive before I can finish them up.
The main-board is much bigger then the last one. Almost 4 times as big, however, for the added features, it's worth it.
I've taken the suggestions here, and went even further. The board now features opto-isolated mosFETs for each switch. In addition, I've added jumpers to allow the user to select normally open switch operation, or normally closed switch operation. In addition, I now have added a jumper to select +5volt pull-up instead of sinking to ground. From my understanding, BoBs like the C10 or C32 require the limit switches to be pulled up to +5volts, instead of sinking to ground. So, that feature has been implemented for each switch.
Also, as you can see, the switches will now be pre-wired with cable.
The standalone switches work beautifully now. And can be selected as normally open or normally closed operation. If the wire is accidentally cut, for example, it activates the software to shut the machine down (only works that way in Normally Closed operation). :banana: Just as in the video above on the prototype board.
I may later, get better opto-FETs to allow more current switching. It's an optically isolated mosFET, but they actually call it an SSR (Solid State Relay). Currently, what's on the switches and boards only allow for AC/DC operation at a max of 60v @ 100mA. That one chip alone is $0.76 when ordered in multiple of 100. Pretty spendy. I did a search the other day, I can get those in the same chip size for up to 40v @ 2A. But, that raises the price of a single chip to $3.00 each. I have to do alittle research and see if those chips would require some type of a heatsink to dissipate the heat that could result from switching a 2A load. If it requires a bigger footprint on the circuit board, then I can't use the chips. If a simple little heatsink placed on top of the chip, via thermal grease or something, then they should work. I'll do some research on that.
As most break-out boards use an optocoupler for the limit/home switching, the opto-FET will only be switching about 10-20mA anyway. But, I could make it an option to upgrade that chip, which could allow separate switching for other applications requiring up to 2A loads. As these are digital Hall Effect Sensors, there's so many applications these can be used for, other than Limit Switches for a CNC.
I am hoping I don't run into any problems once I fire this kit up and test it. In simulation, it works, but in reality it could be a different story. Wish me luck!
If the kit works as intended, I will post a video of it working.
FYI, I'm still working on the schematic, I mean, I have it drawn up, and converted it to the PCB software, but I need to tidy it up and make it look good before posting it.
If the kit works as intended, then I'll post the schematic later, for those who want to attempt this kit themselves. As you can see from the boards, there's alot of chips; almost all of which are logic chips. those can be cut down, or more added, depending on the number of switches you want to use. I decided to go with 8 switches in the kit. But, with this new design, unlike the old design using ULN2803 chips, I am not limited in how many switches I want to use with the kit. By making the board bigger, or smaller, I can and or subtract the amount of switches and just have new boards printed up. The ULN2803 chips, as in earlier design, only allowed me to have 8 switches total.
For those who will ask, 'why didn't you use a micro-controller and shift registers?' Well, I could have, yes, but, I'd be looking at the same size board, or maybe even bigger, as I would have to add transistors to switch the LED's on and off. The logic chips can sink enough current to turn the LED's on and off. Cost wise, is probably about the same. And from what I've been told, Logic Chips will switch faster then a Microcontroller/Shift Register/Transistor layout.
Jason
X²Design&Fabrication
www.x2df.com