Follow-up on the switch controller
Life is crazy, as most people know. After having many delays with my previous project I wrote about getting the boards installed on my father-in-laws train set, I'm proud to announce that he's been very happy with using them and glad he can't accidentally burn out any of his switch motors. While he's not using the tortoise style features I built in, he's been using my boards where he has his relay style switches.
While I've been over there I've also helped him improve how he's been doing his wiring, including giving him a good supply of heat shrinkable tubing to use to help prevent accidental shorts. Never underestimate how much a simple change can improve things. I do admit, I went overboard when I bought my supply on eBay, but I figure having too much in stock will help me be less concerned about the cost of using it, and more concerned with safety, but 100m of heat shrink per size will last a hobbyist like me forever!
Since I last wrote ...
Since I did my previous design, I've done two other boards which I might cover them or related in the future. A current & opto sensor board for the train layout and a simple generic voltage/current isolation board with 8 outputs at up to 1A each with opto isolated inputs. In the near future I'll be helping my father-in-law test the opto sensor portion of my sensor board in a couple portions or his layout where he wants to prevent accidents once he starts using DCC & multiple trains.
Thinking about new designs...
After talking with my father-in-law about DCC and his questions about booster stations, I dug up the specifications for DCC from the NMRA DCC standard and looked at a simple 3A DCC booster design. I admit it, when I look at circuits I'm cheap when I'm worried about the cost of parts, and the LMD18200 seems a bit expensive to use, specially to get only 3A capability!
So, I start digging into H-bridges and half-bridge parts and circuits as well as the parts I already have and use. Since I'd like to eventually be able to handle more the 3A is I need to (both for the trains and myself), I decided that a driver with external FET's would probably be the best way to go since then I gain high current capabilities and can tune a single design based on cost & current requirements easily.
Yes, I know there are good commercial boosters available, but I'm also giving you my train of thought and I like playing with circuits anyways and maybe I'll inspire someone else.
... to switching power supplies?
As a side effect of my research I also got to thinking about some about switching power supplies, and how my test setup, having a couple power supplies with a wide range of voltages and 5 to 10 amps available would be good. High current unregulated supplies are simple, linear regulation over a wide range with 5+ amps usual means heat & heat sinks, cheap switching supplies either don't have the current or are more limited in range (5V-30V 5 amp is the minimum I'll consider for my test bench setup, and 3V to 40+V at 10 amps or more would be sweet). Combine that with the fact I discovered my cheap 2A up to 15V DC supply I bought has a nasty spike on it at 52khz, I think I'll play in this area and see what happens.
Start combining it together
Most switching supply chips can be sensitive to the board layout and/or are current limited, Being a hobbyist, I want a circuit that isn't very sensitive. Since I might have to play with an H-bridge driver in the future, or maybe not. Plus, if you aren't careful with your design, you can easily pickup noise at the frequency that basic switchers run at or a design that isn't very adjustable. Yes, a good engineer can prevent that, but I'm the first to admit I'm not an engineer! How about using a half-bridge driver with a couple MOSFET's as a simple DC to DC converter/switching power supply and I can use a simple unregulated power supply to run several of these to meet my needs? While not something that is commercially viable for me, it'll be something good to play with that will help my setup as well as other projects in the future.
Time to start play and see what happens :D
