I’m finally getting back into designing boards. I just ordered some test boards from OSHPark. Love that site and there low minimums and affordable pricing.
I have been working with Wemos D1 Mini units and need to build a carrier board that supplies power and holds other components. I drew up the pin outline in Eagle and sent it off to make sure it’s right. I find this saves alot of aggravation when drawing my own parts.
Now that I’m designing PCB’s I figured I should look at an upgrade of Eagle. Ruh Roh! Autocad bought them. Autocad makes nice stuff, but the baby from the marriage of CadSoft and Autocad is likely to need time to grow up. They seem to have stopped selling Eagle and are talking about something new. Branding and messaging is a mess and there is annoying pop-up all over Cadsoft’s site. Messy Marketing makes it look like a Walking Dead website. 🙁
Well, that’s as good of an excuse as any to survey the field and see what’s out there. Altium seems okay, but I’m not ready to throw $1k at it and I don’t want a product filled with gotchas and fish-hooks trying to upsell me. I already have Quick(sand)books for that.
Enter KiCad. It’s open source, GitHub friendly, and has a huge number of users. It’s also multi-platform. The price is right, just bits from Comcast which are $120 for 1 TB/mo. 300MB later, I run the installer. There are some features to be desired, like auto-update. It has it’s own set of vexing issues, but the documentation and YouTube videos are really good. There are a number of things that are fundamentally easier to do… such as part design/layout. Other things are awkward at best, such as the inability to set defaults or work with Design Rule files for various fabrication houses. One particular nice thing is that Eagle was always picky about design scale i.e. units/millimeters and was notorious for leaving wires disconnected. KiCad seems to have a more intelligent UI that avoids this issue while being far easier to share design files etc.
Like all PCB design tools, learning curve is a modest description…. I prefer to call it a learning cliff.
So… I learned a bit about RCA and VGA today. VGA is a component input, RCA is a composite input. What does this mean? RCA has the signal all on one wire and the devices that use it separate it electronically. This compromises fidelity, or information density which is why it’s great for 640×480 and TV but not for 1080p or 4K. VGA on the other hand is a component signal, red/green/blue, vertical/horizontal sync etc.
Here is a great image of VGA, courtesy of Instructables: (click to view the article)
I’m not sure how well this would work… it’s a little too good to be true.. but it gives you an idea of what is going on.
Here is a better illustration of the VGA pinout: (courtesy of stackexchange, click to view source article)
Here is a schematic that backs up my hunch that the instructables is too simple. Courtesy of Next.GR (click to visit)
This circuit only generates greyscale…. or black and white video.
In case you were wondering how hard can a video signal be? lol…. it’s complex. Really a marvel of radio engineering. Courtesy of Field Effect LLC, click to follow to article.
I have other objectives than engineering this solution…. and I only need one…. so I bought this on Amazon. (click the image to go to the product)
It offers these modes:
I had some time this evening to assemble a prototype for the power supply. It immediately drew 1amp and started to blow up a capacitor. Not good. I’m not completely sure what was wrong. The only deviation had been using a 1N5818 diode instead of a 1N5822 on the feedback circuit. I don’t think this is critical and it looks like it’s used to bleed down voltage when the circuit is off.
There were a number of minor things wrong, so I incorporated some changes and made v1.2 The input/output headers weren’t labeled and were too close together for screw terminals. The diode pads were drilled too small and too close together, i.e. I used the wrong package size. I also didn’t like the input and output side by side. I also changed the package layout for the IC. I’m not going to bend the thing over on it’s side. That’s silly for this application.
I ordered new boards from OSHPark tonight. Should have them in a couple of weeks.
The new board layouts:
Old board layouts:
My boards from OSHPark arrived yesterday. They look fantastic. I was very tempted to put a bay-light together before bed. It’s my first round board. That’s when I realized I had not ordered the LM7512 12v voltage regulators. I made a quick check of the schemtatic and LED resistor calculator to confirm that I had designed the circuit with a 12v operating voltage. This provides more possibilities in terms of where it can be used than a 24v operating design.
So I skipped the critical part! There was nothing else to do but order them and wait. Tayda is celebrating the “water holiday” which means nothing happens until they get back. If I was in a hurry I’m sure DigiKey or Mouser would have had the part, but I’m not and I like Tayda. They have great prices, super accurate picking, and cheap shipping.
Maybe next week….
Now, my more astute readers may notice the square boards which are OrangePS v1.1. Those boards came in too and I’ll try to get around to assembling them and testing them. This board has lots of possibilities. It’s initially designed to be a very stable 5v power supply for an OrangeOne Single Board Computer…. aka Orange SBC. However, 5v is also the magic number for all number of USB chargers and other goodies. So I may branch the design and create a 5v USB charger at some point in the near future. Yes, you can buy them, but most of them are not designed for 24v input current that is found on my motorhome. Besides, do you *really* think a $2 USB power source uses a design that places voltage stability high on the agenda? I don’t. By the time you factor in middlemen you are talking about a 25 cent item at the manufacturer.
My parts arrived from Tayda this weekend. It’s always fun to receive components and check them in. Boards are shipping today and I should be ready to build prototypes for the power supply and LED projects.
I also received my OrangePi One single board computer. It’s a $10+ embedded Linux PC. 1/2GB of ram, network, a USB port and power.
I ordered this one for about $19 from an Amazon reseller. I also ordered one on AliExpress for $9.99 with free shipping. I plan to print the case for it when it shows up, using the 3D printer. I’m building a power supply for it to use vehicle voltage to power it. That should eliminate the unique barrel connector on the power input. Once I get the kinks worked out I’ll publish the power supply.
Here’s a glance at the schematic for v1.1
The other project is bay-light which is a light with 9 LED’s and a regulator IC so it can be powered by 12-30vDC that is typically found on vehicles. I could have purchased a light for $12 to $20, but I think these will wind up being a little cheaper. Besides, making them is half of the fun.
I found a neat SBC called an Orange Pi. It’s basically a Chinese knockoff of a Raspberry Pi. Similar, but not the same. The problem is that it uses a stupid 4mmx1.7mm plug which is reasonably uncommon. A few folks mentioned removing the power connector and soldering in some wires.
My eventual application is mobile, so I decided I would just design a power supply and fabricate it. A quick trip to Tayda Electronics confirmed that the switching voltage regulators were criminally cheap at 76 cents a piece. All the parts were ordered to build 10 of them for around $18.
I spent a few minutes at lunch dusting off my Eagle skills and drawing the schematic. I then arranged the board and sent it to Oshpark. I’ll receive 3 prototype boards for $6 including shipping. Not bad.
The finished unit will accept 7 to 40vdc and output 5vdc 3A. The Orange Pi requires 5v 2A so this should work just fine.
Here’s a image of what the board should look like.
I expect these to be an $8 kit when I’m done with them. It’s primary purpose is to provide a regulated 5v power supply to a mobile single board computer.
So I had this idea tonight to build a fluid dispenser controlled by an Arduino. The problem I want to solve is dispensing lubricant fluids in metered amounts for my RV. Houdini would like my RV, it’s very difficult to access the filler locations. It’s nearly impossible to add oil without spilling it. A funnel isn’t the easy solution because of the access. My RV is far from being alone with this problem. Almost every Bus has the same headache.
So why not use a pump? Great, but how do you control it? Hmm… well an Arduino with a push button or dial interface and an LCD and maybe a couple of LED’s. Add a printed case and a peristaltic pump and a way to count revolutions and you should be good to go.
Here’s a perfect solution…. a stepper driven peristaltic pump… http://www.aliexpress.com/item/Kamoer-peristaltic-pump-12V-DC/1850266365.html?spm=2114.40010308.4.38.N8z9VZ
Way too expensive though…. $90 plus $30 in shipping for a $20 motor and some tubing… the rest could be 3D printed dirt cheap or fabricated from metal. Would need to include a stepper driver, but that’s fine it solves the metering issue. 320ml/min is about 8oz/min so a gallon would take 8 min to dispense…. that’s fast enough for function.
Here is a $35 version that is about half as fast… http://www.ebay.com/itm/Peristaltic-Pump-Dosing-Pump-With-42-Stepper-Motor-Tubing-Hose-Pump-CN-/361476915848?hash=item5429b40288:g:b2YAAOSwxCxT6ft4 for 1/4 the price.
I think this is doable. I’ll look into it when I have time later this year.
Add a container like this to dispense from: $35
A small LCD like this: $9
A rotary encoder: 76 cents
and a start / stop button: $1.50 or less
I think it’s pretty do-able. I’ll definitely get back to this because putting oil in the engine is a nuisance and it has to be done every 1,000 miles or so. It’s just part of running an old Detroit Diesel motor. They leak, eat oil, and smoke a bit when started, but run forever and are easy to maintain.