Post by thread:What design tools to use for PIC projects?

All the recent talk about AP circuits inspires me to ask: what is a good tool for a hobbyist to use for doing PCB layout? APC offers Easytrax, is that a good product? I've finished my first project, a servo controller. It mostly works, but there is some unreliability, which I suspect is from motor noise and power dips when motors start up. _Mobile Robots_ suggests that these problems can be solved by putting a capacitor from power to ground, but they don't specify the size. Can anyone recommend a good size to start with? If I had a big box o' capacitors, I'd do the experiment myself, but I'm just starting. Thanks, Brian

Brian Scearce wrote: > > All the recent talk about AP circuits inspires me to ask: what is > a good tool for a hobbyist to use for doing PCB layout? APC offers > Easytrax, is that a good product? > > I've finished my first project, a servo controller. It mostly > works, but there is some unreliability, which I suspect is from > motor noise and power dips when motors start up. _Mobile Robots_ > suggests that these problems can be solved by putting a capacitor > from power to ground, but they don't specify the size. Can anyone > recommend a good size to start with? If I had a big box o' > capacitors, I'd do the experiment myself, but I'm just starting. > > Thanks, > Brian .01uF soldered directly to vdd_vss for noise the dips depend on to many factors to guess just double what you have.Providing the supply can charge this filter cap before the power up timer on the chip times out you will be ok.As to the software try at least 3 or 4 before investing.Alot of the satisfaction or dissapointment depends on your previous experiences and expectations. Most vendors have demo's you can download and try.

At 11:56 AM 5/8/97 -0700, you wrote: >All the recent talk about AP circuits inspires me to ask: what is >a good tool for a hobbyist to use for doing PCB layout? APC offers >Easytrax, is that a good product? Never used Easytrax. I use SuperPCB from Mental Automation, generally pleased with results. http://www.mentala.com >I've finished my first project, a servo controller. It mostly >works, but there is some unreliability, which I suspect is from >motor noise and power dips when motors start up. _Mobile Robots_ >suggests that these problems can be solved by putting a capacitor >from power to ground, but they don't specify the size. I've done quite a bit with servos. Make sure you have VERY heavy traces to provide power to the servo. Include a series resistor on the signal out of the PIC. 270 ohm minimum, max varies with servo brand, 10K is reasonable for most, would go as high as possible if I were you. If in an RF environment, I suggest using standard strategies to reduce noise - chokes, caps, shielding, etc. Andy ================================================================== Andy Kunz - Montana Design - 409 S 6th St - Phillipsburg, NJ 08865 Hardware & Software for Industry & R/C Hobbies "Go fast, turn right, and keep the wet side down!" ==================================================================

> > At 11:56 AM 5/8/97 -0700, you wrote: > > >I've finished my first project, a servo controller. It mostly > >works, but there is some unreliability, which I suspect is from > >motor noise and power dips when motors start up. _Mobile Robots_ > >suggests that these problems can be solved by putting a capacitor > >from power to ground, but they don't specify the size. > > I've done quite a bit with servos. > > Make sure you have VERY heavy traces to provide power to the servo. > Include a series resistor on the signal out of the PIC. 270 ohm minimum, > max varies with servo brand, 10K is reasonable for most, would go as high > as possible if I were you. If in an RF environment, I suggest using > standard strategies to reduce noise - chokes, caps, shielding, etc. > > Andy > Is the purpose of the serial resistor to lower the voltage of the PWM signal? I've been using a PIC to control 3 servos on my Inchworm robot for the past 9 months and I don't use a serial resistor, but I do use a higher voltage for servo power than for the PIC, which naturally makes the PWM output a lower voltage than the servo power. Initially, I was observing instability in the servo when the PWM signal was the same voltage as the servo power. Then I checked out the PWM signal with an oscilloscope and discovered that it was about 0.3 volts lower than the servo power voltage. So I started using 5.3 volts as the servo power volgage and the instability was gone. Of course, I now use 5.75 volts as the servo power voltage because I want to get more power out of the servo. I'm thinking of going to 6 volts on my next design which, I've heard, is the absolute max for servos. Can you confirm this Andy? Keith Keith D. Kotay Ph.D. Candidate Dartmouth College spam_OUTkotayTakeThisOuTcs.dartmouth.edu http://www.cs.dartmouth.edu/~kotay

Brian Scearce wrote: > > All the recent talk about AP circuits inspires me to ask: what is > a good tool for a hobbyist to use for doing PCB layout? APC offers > Easytrax, is that a good product? > > Brian, Since I'm sort of a hobbyist myself, I may see things more from your angle. About EasyTrax by Protel: Probably the only FREE product. Alas, it runs under DOS, which disqualifies it for me. Drivers for common printers and graphic cards are included. An alternative is: 1. Protel Advanced PCB. (http://www.protel.com). Fully working demo, but limited to 200pads or 20 components. Takes some learning, but is excellent i.m.o. You can have more than 20 components if you draw them using discrete pads. Might be a good idea learning this one if you plan to work in the industry. Note that it is licensed for evaluation only! I don't think anyone would mind if a hobbyist makes one or two PCBs for his own use, though. The full version is expensive, so perhaps you want to read on: If you're prepared to pay a wee bit, there are two good alternatives, both very intuitive. 2. PIA. (http://www.waldherr.com) About 70 USD, If I remember right. Nice. Definitely worth the buck (quid?) and good enough for a hobbyist. Look at the downloadable demo! Save disabled. 3. SuperPCB by Mental Automation http://www.mediawhse.com/mentala/mentala.html). Definitely nice. Save disabled in downloadable demo. Price is like 170 USD or thereabouts. Used and recommended by several subscribers to this list. My PCB strategy is to make single-sided cards, with most components on the component side (how about that) but all resistors surface-mounted on the foil side. Since the PIC has centralized power leads, it's easy and advantageous to fit a surface-mounted 0.1uF cap under the PIC, between Vdd and Vss. If you haven't tried SMD and don't have ready access to components, I'll gladly send you coupla hundred resistors for nothing. Mail me directly, not the list. Good luck Gustaf

At 14:44 10/05/97 +0200, Gustaf Tham <.....gthamKILLspam@spam@lidkoping.mail.telia.com> wrote: >My PCB strategy is to make single-sided cards, with most components >on the component side (how about that) but all resistors >surface-mounted on the foil side. Since the PIC has centralized >power leads, it's easy and advantageous to fit a surface-mounted 0.1uF >cap under the PIC, between Vdd and Vss. If you haven't tried SMD and >don't have ready access to components, I'll gladly send you coupla >hundred resistors for nothing. Mail me directly, not the list. I never have done SMT, but I'll have to do a couple of prototypes now, and it seems you have some "hobbyist experience" with that :-) How do you mount the components? Is it feasible to mount SMT resistors, and even SOIC packages manually? Any special techiques, precautions? Thanks, Gerhard

Gerhard Fiedler wrote: > > At 14:44 10/05/97 +0200, Gustaf Tham <gthamKILLspamlidkoping.mail.telia.com> wrote: > >My PCB strategy is to make single-sided cards, with most components > >on the component side (how about that) but all resistors > >surface-mounted on the foil side. Since the PIC has centralized > >power leads, it's easy and advantageous to fit a surface-mounted 0.1uF > >cap under the PIC, between Vdd and Vss. If you haven't tried SMD and > >don't have ready access to components, I'll gladly send you coupla > >hundred resistors for nothing. Mail me directly, not the list. > > I never have done SMT, but I'll have to do a couple of prototypes now, and > it seems you have some "hobbyist experience" with that :-) > > How do you mount the components? Is it feasible to mount SMT resistors, and > even SOIC packages manually? Any special techiques, precautions? It's easy, provided you have good vision, steady hands and a good soldering iron with a thin pointed tip; I use a temp. controlled Weller. Thin, good quality solder. And if you have a nylon shirt, rubber sneakers and your hair on end, I suggest you wait for a rainy day :-) I know of three methods: 1) Pre-tin one of the solder pads of the card. Hold the component with a pair of pointed tweezers (I got one which was discarded from ophtalmologic surgery, but we can't all be lucky) pressing it firmly against the PCB while re-melting the solder. Now, the other end of the component: Do a normal soldering, heating component and foil at the same time. When the tin melts, let just a little "capillarize" under the component. You might turn back to the first joint and re-solder with fresh tin. Use very small amounts of solder! This is how I do it. The gurus of this list may whince and faint, but who cares. 2) Hold the component in place with a weighted arm type thing. 3) Glue the component in place before soldering. Note that Murphys law is particularly powerful here: The stronger the glue, the more likely you are to use the wrong component. Yes, you can do SOIC packages, too. I did, but at the moment I find the "hybrid" method I told you about better, since I use ordinary push-buttons and other stuff that go on the top side anyway, and I like that SMT cap under the PIC. Cheers Gustaf

I've been using the CAD system from Advanced Microcomputer Systems in Florida for at least ten years. I've done lots of designs with it and am quite satisfied. It includes schematic capture through board layout. They have a web site with demo software, but I don't recall the URL right now. Try a search and you'll find them. Harold Harold Hallikainen phone/fax/bbs +1 805 541 0201 Hallikainen & Friends, Inc. web http://slonet.org/~hhallika PO Box 4737 email .....hhallikaKILLspam.....slonet.org San Luis Obispo, CA 93403-4737 email EraseMEhhallikaspam_OUTTakeThisOuTbroadcast.net USA email ap621spam_OUTcleveland.freenet.edu

At 11:16 AM 5/10/97 EDT, you wrote: > I've been using the CAD system from Advanced Microcomputer >Systems in Florida for at least ten years. I've done lots of designs >with it and am quite satisfied. It includes schematic capture through >board layout. They have a web site with demo software, but I don't >recall the URL right now. Try a search and you'll find them. > I have used this for about 5 years. It was about $250. I think they have a Windows version out. Like all PCB programs it has its quirks (the parts library system is bad IMHO). I bought it when I was consulting. It was the only program I found at the time that bridged the gap between low end hobbiest and larger ($) systems. It is quite possible to do professional quality layouts on it. Despite the irritating library and rather poor customer service it was a pretty good value for the cost. - Gary ------------------------------------------------------------------------ Gary Sutcliffe, W9XT Unified Microsystems @spam@ppvvppKILLspammixcom.com PO Box 133 Slinger, WI 53086 http://www.qth.com/w9xt 414-644-9036