Circuit design for the motivated beginner: How to proceed?
jamma
Posts: 33
Electronics are a new area of interest for me (my skills lean toward mechanical design and fabrication, although I'm relatively comfortable with programming). A CNC project has forced me to dive head on into this world, and I'm in need of some tips to start out.
For example, I have a need to route the output of my drives on the basis of a three-position switch: e.g. "Off | Mill | Lathe". When "Mill" is selected, one group of output terminals become "live", when "Lathe" is selected, a different group becomes live.
I could almost handle this if all outputs were 5V TTL signals (I've done some Stamp projects and am currently playing with the propeller). Unfortunately, only 7 of the 9 are. The other two drive the motor at up to 80VDC @ 20A. This is clearly beyond simple signal switching, and I don't have the experience in power circuit design to figure out how to proceed.
Another, perhaps simpler puzzler for me is how to take a 17VDC, 4A unregulated signal and produce both a 5VDC & 12VDC regulated signal from it. Presumably, it's a matter of finding suitable voltage regulator ICs, but even approaching a simple circuit like this·completely solo has me a little nervous.
I realize a Parallax forum might not be the right place to post such questions, so what is the appropriate place? While I'm open to book suggestions (and am plowing through a ton right now), I really appreciate the human interaction and practical advice that are best found on forums. Any suggestions? Are there professionals out there who offer design services for simple stuff like this at reasonable prices?
Thanks in advance for any tidbits you're able to throw my way.
For example, I have a need to route the output of my drives on the basis of a three-position switch: e.g. "Off | Mill | Lathe". When "Mill" is selected, one group of output terminals become "live", when "Lathe" is selected, a different group becomes live.
I could almost handle this if all outputs were 5V TTL signals (I've done some Stamp projects and am currently playing with the propeller). Unfortunately, only 7 of the 9 are. The other two drive the motor at up to 80VDC @ 20A. This is clearly beyond simple signal switching, and I don't have the experience in power circuit design to figure out how to proceed.
Another, perhaps simpler puzzler for me is how to take a 17VDC, 4A unregulated signal and produce both a 5VDC & 12VDC regulated signal from it. Presumably, it's a matter of finding suitable voltage regulator ICs, but even approaching a simple circuit like this·completely solo has me a little nervous.
I realize a Parallax forum might not be the right place to post such questions, so what is the appropriate place? While I'm open to book suggestions (and am plowing through a ton right now), I really appreciate the human interaction and practical advice that are best found on forums. Any suggestions? Are there professionals out there who offer design services for simple stuff like this at reasonable prices?
Thanks in advance for any tidbits you're able to throw my way.
Comments
When you talk about a 17VDC unregulated signal, are you talking about a power source for the digital circuitry? If it's electrically very noisy, you might want to consider another source.
There are all sorts of regulators available. Which one to use depends partly on how much current you want to draw from it. If you need 1A or less, you could use the examples on the Stamp development boards. They're well documented and tested. Look at the datasheets and application notes for the regulators for other examples and suggestions. Generally, these are available from the manufacturer's website - often much more information than you need. If you need both 12V and 5V, you might run the 5V regulator off the 12V regulator output to reduce the amount of heat the 5V regulator has to dissipate from the 17V source.
If you're just using the 17V source as a signal, then a simple voltage divider might do since the amount of current drawn by a chip input is neglectible.
Consider a relay for switching the 80V @ 20A. There may even be some solid-state relays suitable for this kind of load.