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#26119 How to draw 220V motor

Posted by Bill E. on 30 March 2012 - 12:34 AM in General Discussion

Netizens! That's clever. I love it - we should cap on that phrase.

Rookie, exactly what do you want to do with the 220V (AC I presume) 100W motors? Control their cycle time or speed? Cycle time can be done with triacs (for a reasonable duty cycle period like on for 10 seconds off for 10 seconds) but if you want speed? Now that's more difficult. Magpie hit it on the head that if you want to control the speed of the motors. PWM is all about effective energy delivered to a load. Using PWM with AC (50/60HZ) just doesn't compute. You need DC motors to work with PWM - on vs off time.

A solar system, I would think, doesn't need milisecond or even second control. If I were you I would think about a NUCH hegher repetition rate line MINUTES control of the pumps. Simple monitoring works then.

Peace,
Bill



#26118 Getting Started with...

Posted by Bill E. on 29 March 2012 - 11:59 PM in General Discussion

Hello Edward and Chris! I have the pdf version of the "Getting Started with Netduino" - that is how I recommend getting the book. I received an email alert from O'Reilly media today announcing the "Getting Started with Netduino" for $7.99. $4 less than I paid. A great deal. For all of you that read this post I encourage you to jump on this! It's well worth it for refresher/beginners (me!), etc. I think this publication is the fill-in for the "Getting Started with the Internet of Things" that references the Netduino Plus. As an experienced hardware guy I would love to see the Netduino expanded to use ALL of the available I/O be accessable within the .NetMicro scope. In fact, using a much biggr MCU for a Netduino would be really cool! More I/O pins available than the Arduino pinout. Kinna like the Arduino Mega. Or more. Any plans for that? Chris, I commend you on your book. It is a very informative publication. Written in the Maker style, yes, which is a bit "Radio Shack-ish" but it gets the info across which is the main thing. Kudos!! Get the book, readers!! Peace, Bill



#24581 Getting Started with Netduino book

Posted by Bill E. on 23 February 2012 - 01:25 AM in General Discussion

I haven't posted on this forum for quite a while so bear with me. Chris' book was delayed for over a week. Anyone have any insight on this? I have an Amazon.com gift cert that is just aching to be spent!! I have been (patiently) awaiting the release of the book since 2011. Teaser! Get your book published soon Chris. I am really looking forward to its release. I was hoping to be "back in the saddle" with Netduino after Chris' book - now I am going away for two weeks!! Whoo-hoo and Awwwwwww!!!!! I guesss I have to wait - some more ...... Bill



#18921 Use IR Remote

Posted by Bill E. on 08 October 2011 - 12:54 AM in General Discussion

As I sit here thinking of how to reply to your question of a "scope" I have to kind of step back and apologize for presuming. As a hardware guy I presume everyone has a scope. A TV remote, as Stefan elaborated on, can be of, oh, maybe 500 different varieties. The basic operation, however, is all the same. Without a scope though this could turn into a real nightmare! I really don't know how you could reverse-engineer a TV remote with a meter. Can you consider a matched set of receiver/transmitter components for your project? It would be possible if you follow the specs of the individual transmitter/receiver parts. It would be simple if you started with a matched set. See my post about "A Hardware Guy Drowning In A Software World". You will find the design files for this. I called it the Collision detector. The components would work for you. Good luck with this. Regards



#18886 Use IR Remote

Posted by Bill E. on 07 October 2011 - 01:34 AM in General Discussion

Hello Abdalla and, Welcome to the forum (As Stefan said). I use IR remote emitters and sensors in my - yet to be sucessful - autonomous bot. The receiver I use is a generic 38khz device and an Osram emitter LED at 980nm (i think) (watch for the IR frequency, the nm or wavelength of the emitter & receiver). Do you want to use a TV remote? Make your own remote? It's all possible. The most common frequency of "modulation" is 38khz. Get an InfraRed receiver LED or transistor which has a relatively wide bandwidth (800nm to 990nm),connect it up to a scope and fire away at it with your TV remote. If any of this confuses you just post back and I will (or the community will) respond. Great question. This is a wonderful lead-in to specification sheets. Good luck! Regards.



#18884 How to read values from an analog sensor ???

Posted by Bill E. on 07 October 2011 - 01:12 AM in General Discussion

Beowolf, how accurate do you need to be? I ask this because the interrupt method is the best way to go about precisely counting 3900 ppl (pulses-per-liter) but which begs the question: How fast is the flow? How many lpm? LPH (per hour), etc like Stefan did. I have a fish pond and I am interested in measuring flow from my pump(s) back to the pond. The "vane sensor" or hall effect sensor is a nice way to measure flow but you suffer from having to be responsive to the individual "ticks" of the sensor. If your CPU, in this case, a Netduino, is doing a lot of other things, you may not be able to deal with the latency, or delay, of handling many interrupts. I am an interrupt nut - I love them! But if you only need an average of the flow (which is what most people care about) why not convert the pulses to analog?? Integrate the pulses with an RC network and simply read the analog value from the RC. Over hours/days/weeks/..., this may be the best way to do this. Place a resistor in series with the sensor output and a capacitor to ground after that (your sensor must have a rail or "potential" level for this to work). Use the A/D to measure the capacitor level and, viola! You have an average of the flow! I believe in the "KISS" approach (KeepItSimpleStupid) whenever possible. Choose the R & C values emperically, that is trial and error - to what suits your needs. Good luck and let us know how it works out? Regards.



#18567 5V Relay Driving Circuit

Posted by Bill E. on 29 September 2011 - 01:48 AM in General Discussion

Charlie, what do you think your duty cycle will be on your boilers? That is, how long will you have them heating vs not-heating? And, I have to ask this, where in the world are you getting the power to energize 39AMPS@220V worth of power supplies?!! Thats ~ 8600 Watts!! Never mind - don't answer that!!! It's best we don't know, I think... ;-} Fire is always a possibility when high energy sources are used. Good going with the fuses. Transistors will burn, fiercely, at high currents. "I love the smell of burning transistors in the morning!" Possible scenario - cycle the heaters. Never have more than one on at a time. Now you can run from standard 30A 220V mains. If you are simply turning on and off heaters (I assume they are water tank heaters?) then consider triacs. A lot cheaper than relays feeding relays. You could use MOSFETs to turn on the triacs. When PC boards are manufactured there is a process called "profiling" the process. Boards go through multi-zone ovens which melt solder at specific temperatures. One part of the process is considering the residual energy left at a zone in the oven. That means the PC board will carry heat from the zone so you want to consider that into the equation for the next zone, and so on. Point being, can you determine how long a heater will continue heating AFTER you turn it off? That will determine your overall duty cycle. Good luck, and I would love to sample some of your brew!! Regards, Bill



#18566 Power filtering capacitors on prototype shields?

Posted by Bill E. on 29 September 2011 - 01:07 AM in General Discussion

I wholeheartedly agree with Mario. The 100nf (or 0.1uf as we call them here in the USA but I think that is slowly changing as we align with the rest of the civilized world!) are actually noise "decoupling" capacitors AKA filter caps. Electrolytic caps with high uf values do the job of "smoothing" out ripple on a DC source while small value caps, like the 0.1uf (100nf) to 0.01 (10nf) caps tend to shunt quick, rapid, spurious noise spikes to the opposing lead/wire thereby decoupling these spikes from your power rail. A really good rule of thumb is: a capacitor acts like a short (low resistance) to AC but an open (high resistance) to DC. The lower the value of capacitance leads to a faster response to change. EE98 here. Always be cautious of the VOLTAGE rating of a cap. Make sure you allow at least a 25% overhead on that value. This question is actually quite a good one. A good topic for a forum, Spork. If you are certain that you will never have anything tied to the 5V pin of the shield then you would not need any decoupling/filtering on that pin. But, why not mount the cap? It's small and comes with the kit anyway. Just in case. The last thing you want is to have your entire shield stack "go into the weeds" because of a motor or relay or remote ESD discharge, right? A bag of 0.1uf (104 marked on the cap body) should be a mandatory item in any designers box. Regards!



#18411 5V Relay Driving Circuit

Posted by Bill E. on 26 September 2011 - 01:33 AM in General Discussion

Charlie M, you have received a LOT of good info from the members. From my experience, use a darlington transistor as a relay switcher for a microcontroller. The TIP102 would work for probably starting a car!! An MPSA12 will work for your apps no problem. Microcontrollers are very good at handling "hysterisis" issues. All schmitt outputs are good at that. Please research that as a side issue. Whenever I come across a switching issue with relays (unique animals, I have to admit) I immediately go with a darlington and a "flyback" diode. Your pdf circuit is perfectly accurate and will work fine. Opto22 used to make SSRs that were "digitally" controlled. I haven't used them for MANY years so you will have to look them up yourself. The Mini or any micro should be able to turn them on and off. Major point here: what will happen if your transistor shorts? Semiconductors shorting is the "norm" of their failure modes. If the switch shorts then the relay will be on all the time. Consider a "back-up" secondary switch or a fault-redundant switch. You wouldn't want an IV circuit to be injecting drugs into your arms because of a cheap, simple transistor failing. Or, in the case of your kettles, you would not want your house, or brewery, burning down because of a $.05 transistor! Another example of my concern with good people mucking with household mains. Really serious stuff! Charlie! Good luck and post again if you have a tech question. What a good one you put out!



#18269 Noobs guide to connecting parts to a Netduino

Posted by Bill E. on 21 September 2011 - 12:33 AM in General Discussion

JohnnyBoats, What an excellent link! Good find. As an EE I read the first few "how to" articles word-for-word. After that I was skimming through very fast & having my eyes "roll-back" with the tech details. No dis-respect!! No way! I appreciate and admire the content, author, your mention of the link. First off, I just returned (less than 48 hours ago) from a 2 week vacation trip to Japan and am still in a "jet-lag" stupor. Second, I am SOOO glad to be back & getting back to the forum. For the folks that can't follow, or cannot grasp the tech-details of the link, allow me to add my 100 yen (that's about $1.40 now!). 1. Our microprocessors/microcontrollers have a huge number of I/O pins which is so fantastic!! But watch for the total, combined I/O current consumed (which means POWER produced). That is, if every pin can sink/source, let's say, 25ma, and you are driving 100 LEDs, you can potentially be asking the IC (microcontroller) to deliver 2.5 Amps and, sad to say, ain't going to happen. Ohm's law works for voltage, current, resistance, power, uhhhhmmm, did I miss anything??. Look at the spec sheet for the particular micro for "total current used" or similar. This doesn't mean diddly for inputting to the micro. 2. Really be aware of the input "VOLTAGE". Remember, CURRENT is derived from the resistance between the source and, for lack of a better term, GROUND (or REFERENCE). If you have 100 Volts "across" 10 million ohms there cannot be more than 10 micro amps of current flowing through that resistance. BUT there is still 100 Volts "potential" aross that resistor. Internally to the micro IC, it will violate in a BIG way its circuitry and end up in major smoke. Look at the Parallax BS2 "Serial" input specs. The pins can tolerate a negative 12V to positive 12V signal and still survive because the current and voltage specs are within the PICs "input" specs. Jet lag babbling now! Post your questions/comments & let's see if we can design the next generation space shuttle!



#17421 General Structure for my Netduino Tutorials

Posted by Bill E. on 02 September 2011 - 01:20 AM in General Discussion

Michel, I will certainly be looking forward to your tutorials! Is this the bridge that so many of us are looking for (the C# grail)?? As for me, I will be gone for the next two weeks to JAPAN!! I am taking a well deserved vacation and, I am very happy to say, I will NOT be thinking of Netduinos, robotics, C#, email, work, ... you get the idea! Just good beer, hot springs, great food, sights. When I get back I will be on alert for your tutorials. Way to go, Michel. Much appreciated (more than you think). Regards



#17420 Vibrator Circuit - Need Help

Posted by Bill E. on 02 September 2011 - 12:55 AM in General Discussion

Hi Dan. June, eh? I will remember that. Everyone else got that? I still see no response from TKOTC. I sure hope he didn't try out his circuit! When I built an "arc furnace" with, get this, D-cell battery carbon rods (from the inside of the batteries), a salt-water "rheostat" (now THAT was smart!) and a clay flower pot as the "containment vessel" (search arc furnace, science project, etc.) AND of course the 115VAC mains, back in, ohh, 1965(?) when I was young and stupid, (Oh My GAWD!!! I found the plans here! : http://redneckfabric...php?topic=486.0 ) I was very lucky to survive that one! Us kids in the 60's got away with so much!! My Dad found out what I was doing & freaked OUT (he was an EE)!! Especially when the house lights dimmed and the power meter went beserk! I thnk I caused the, was it 1964? "Great Blackout" on the east coast with that! That was, I have to admit, really fun and radical. I can use that excuse to explain that I am the way I am today because of ... Still on-topic: my point being I was really lucky! And think what I could have done with a Netduino!! Regards.



#17419 Vibrator Circuit - Need Help

Posted by Bill E. on 02 September 2011 - 12:33 AM in General Discussion

We aren't that much different than the lower 48. We just have longer winters and shorter summers. Winter typically starts mid September and runs till mid April :( Oh, and its dark here, at the winter solstice the sun comes up around 10:30 and sets around 3:30 :(.

When you come, come in the summer time. June is a good month, not to hot, its usually pretty sunny. August is the worst time, it rains almost every day. In fact, last year it rained every day for 36 days in a row :(

As to being a PITA on the mains issue, I don't think you are. People need reminders sometimes that the mains can hurt you :-)

-dan




#17366 Vibrator Circuit - Need Help

Posted by Bill E. on 01 September 2011 - 01:24 AM in General Discussion

Dan, I am humbled. Anchorage, eh? Makes my winters in R.I. seem like the Bahamas. On my bucket list I have "trip to Alaska". I hear many good things about your beautiful state. I will get there someday. You are spot-on on the colors. "Black-on-Brass" "White-on_silver". When wired corerctly WHITE & GREEN cannot kill you. But, Never trust the colors. Am I being a PITA about this subject? Regards, Bill



#17298 A Software guy drowning in the Hardware world...

Posted by Bill E. on 31 August 2011 - 01:07 AM in General Discussion

A big sigh here. I know what Moskus is feeling. And I am at a loss as to where that "something in the middle" is. I tried to explain my thoughts for the last half hour in this reply and then just deleted it all because it was becoming so garbled and sounding like gibberish. I am anxiously awaiting Chris's book release. The "Internet of things" book just didn't do it for me. Maybe Chris's book will? Maybe it will simply "click!" for me? Give me my soldering iron!!! My kingdom for a roll of solder! A damp sponge. Needle nosed pliers and diagonal cutters. Spec sheets rule!! Regards all! Bill



#17296 Vibrator Circuit - Need Help

Posted by Bill E. on 31 August 2011 - 12:17 AM in General Discussion

Thanks for the kind comment, Mario. Yes, I thought very hard about what I wanted to say in that reply of mine. I cannot emphasize enough about being very respectful of household mains voltage. Enough said about that! Dan, I feel your pain! I had to chuckle about the engine block heater! Your bio doesn't say where you are at but I remember well the "dipstick heater" from my youth in Rhode Island! What are they? 100W? Not much good when the temp is at -20 degrees... Good points about the safety switch, aka GFI (or Ground Fault Interruptor). But it only works when the wiring is correct: in the U.S., the AC Neutral to the large, wider slot, the AC Line to the shorter slot, and a GROUND to the half-moon slot. Get the line & neutral reversed and your at risk - even with a GFI. When I lived in Germany, the locations were determined by relative location to the ground lug. It is easy either way to mis-wire by a "do-it-yourselfer". Regards.



#17254 How Do I Calculate Resistor Value

Posted by Bill E. on 30 August 2011 - 02:06 AM in General Discussion

Hello Inquisitor! It seems that you have the LED figured out. The photo transistor only needs to be satisfied as to its minimum requirements. To tell you the truth, I haven't found a sensor that is not so sensitive that a 100K resistor (!) would not work with a microcontroller input. It's all in the betas and "transconductance" (ugghhh!), ... The LED is key. The higher the resistance value between the collector and power bus (+5v?) the lower the current needed. BUT the higher resistance will lower the response time. And vice versa. There is always the "transconductance" value - eyes rolling back into head! Just be sensitive to too high a resistance on the transistor collector - heck, you could get into the hundreds of Kohms or even megohms. For hackers & micro dudes, I would keep a stash of 1K, 10K, 100K, 220 & 350 ohm, resistors. That will do you very fine! Everything "digital" can be handled with these resistors. Regards.



#17251 Vibrator Circuit - Need Help

Posted by Bill E. on 30 August 2011 - 01:21 AM in General Discussion

I haven't seen any responses to this post by TKOTC since Aug. 17. I hope you are allright? I am always worried when someone wants to start using the mains AC power from a wall outlet in a project. Call me a worry-wort! I have a relative who is building a "device" that distills fermented stuff (whatever it may be!) into, for the sake of this post, "alternate fuel". Use your imagination and you can figure out what it is. He needed to control a water heater heating element, a 1500 to 3500 watt device, and was looking for advice. I did give him some - reluctantly. He is still with us!! There is available, on the web, a ton of posts about building a "device" for distilling fermented stuff. The majority talk about using a triac, a potentiometer, capacitors, lugs, etc. That is a good way to do it. The problem I had was the lack of warnings and cautions to the reader of getting their butt fried by 220VAC! Or 115VAC for that matter. There was very little warning of using an "isolated tab" triac, et al. So I send this advice with a degree of consternation. An SCR is an ideal device for the half-wave vibrator. You do, however, need a method to "remove" the electrical circuit in order to shut an SCR off. You cannot do it via the gate terminal. You will need an intermediate "switch", or equivalent, to do that. MOSFETs won't work like you think when switching AC. The IGBT is, for lack of arguement, nothing more than a power MOSFET with a bipolar transistor controlling its gate. You could use a triac followed by a rectifier (big enough to handle your load(s)) to run the vibrator. A triac can be turned on and off with its gate. Use the opto-isolator with the netduino. Please, PLEASE be careful!! I cannot scare you enough about working with mains. If you were an electrician, or a disciplined timkerer, well, then you know the way to do this and, possibly, how it feels to get knocked on your keester by mains voltage. But for a beginner, I am "discouraging" you to mess with this without having a CPR qualified partner nearby. I am SERIOUS about this! Mains AC is not to be fooled with! I am speaking from experiene. And, yes, I am CPR qualified. If anyone on this forum disagrees then you are: 1. Lucky 2. Never fooled with mains AC 3. An experienced Electrician that doesn't care about anyone else 4. Misinformed about the pain, physical mutilation, agony from electrical burns 5. Add your own description By itself, a Netduino cannot harm you. You can put your tounge on it and it will only (probably) stop working. No big deal. You won't feel a thing. Playing with high voltage (anything over 32 VAC/VDC is high voltage to me!) will bite you! Bad. And, you do NOT want to experience that. It takes less than (if I remember correctly) 8 ma of current to the heart to stop it. Your mains circuit breaker is normally 10 or 15 AMPS! Enough said. Be careful. BE CAREFUL!! I don't want to hear about anyone, eecially on this forum, being hurt by messing with something that they don't understand. I would like a similar post to ALL members warning about fooling around with household AC. Again, you do not know what you are dealng with if you are an amateur. Bad mojo. Ask a pro or a friend experienced with AC. PLEASE!! All my best regards, Bill



#17219 Proto Board or Perf Board

Posted by Bill E. on 29 August 2011 - 12:25 AM in General Discussion

From a hardware guys point of view, you guys are really on the spot! The "breadboard" (or "proto") approach is indeed still used by professional designers. It is a wonderful way to verify and obtain "proof of concept" - that is, up to a point. Really high-speed stuff just won't get off the ground with a breadboard - you need simulators and raw gut-feel design discipline. But I digress ... You just can't beat the breadboard (or protoboard) for the stuff we all want to do. I use it all the time and it works very well. Get your idea working on a breadboard then (sorry Mario! Your wife will be angry) get the soldering iron out & wire it up on a perf board. For simple stuff I do my own PC Boards, aka PCBA's, or lay out a board for fabrification at a board house. That is very advanced "hardware" stuff that is an entire topic in itself. Hmmm. Maybe we can ... Regards.



#17214 Help with Proper Servo Driving

Posted by Bill E. on 28 August 2011 - 10:21 PM in General Discussion

Inquisitor, Good questions. For the V7805-500, you don't have to worry about going even to the maximum input voltage. The device is a very small "switch mode" power supply and by its nature wastes almost no energy when used within the specifications (the "effeciency"). Just like Chris Seto's reccomendation of the BEC. By the way, that was really a nice bit of advice, Chris! Way to go. I will remember that. Remember that the mini is a 3.3V device. The 5V is only for the 3.3V regulator and outside (external) circuitry. The mini cannot output a signal at 5V and any analog conversions will be done at the ADVref value, which is 3.3V. As long as you maintain the minimum input to the 3.3V regulator (it is a 1V "low dropout regulator" I know - details!) which will be 4.3V you will be fine. The 5V regulator won't care. So, no re-calibrating will be necessary. The more filtering between the mini "brain" and the servo motor the more likely you are to continue operating. A servo is not as noisy as a lowly brushed DC motor but the muscle of the servo IS a brushed DC motor! You say 5 minutes of operation is all you will require? If so, I would go with the linear regulator (LM7805) and not worry about effeciency. Power the mini and LM7805 with the 9V battery and the servo from the output of the LM7805. An alkaline 9V battery has about 500mAH (1/2 AMP capacity for 1 hour) so for 1/12 of an hour I would think you could use a cheap 9V sacrifical alkaline battery. Mario's explaination was a very good one. No-one can figure out how to escape the laws of Mr Georg Ohm! Not yet, anyway. It sounds like you are well on your way in this project. All the best. Let us know how it works out! Regards.



#17210 A Software guy drowning in the Hardware world...

Posted by Bill E. on 28 August 2011 - 08:30 PM in General Discussion

I am a bit disapoionted that my earlier post was interpreted as "discouragement". The last thing I want to do is discourage anyone from learning/accomplishing/succeeding. From my perspective I read Moskus' post as one that was looking for, perhaps, other peoples ideas, opinions, learning from others mistakes and pitfalls? I stand enlightened now realizing that I kind of forgot that this is a "Netduino" forum and the audience is likely well versed in C#. After reading Inquisitor's reply about "such a book" I was going to send a list of books that I bought waaaay back in the mid 80's from, of all places, Radio Shack called "Engineer's Mini-Notebook" by Forrest M. Mims III. But, I see from Mario's reply that he found the same material in an all-in-one book. Good catch Mario! The web page for Mims is: http://www.forrestmi..._notebook.html. This may tell you that I go way back. Really. Way back. Another handy "reference" is called "Ugly's Electrical References" by George V. Hart. See: http://www.uglys.net/Electrical.aspx My version is from 2002 and, yes, the same rules still apply today. Some local codes may have changed but ... It would be interesting to get some feedback from members as to why they zeroed in on the Netduino. As for me I was drooling at the prospect of being able to use a microcontroller with managed code! Internet, mass storage, USB ... What a great idea. I first saw the GHI hardware which eventually led to the Netduino and I was hooked. Now, like Moskus, I have a hard time getting it to do anything. I am so envious of people with a programmers mentality. Oh well. I liked JonnyBoats reply. I know that, being a Ham, you are indeed bridging the two worlds! I never liked the antenna stuff though. An interesting "outside looking in" observation. The laws of physics (thus electricity) do not change neither do the laws of logic. It still requires an on or off/1 or 0/yes or no to make a logical (digital) decision. If ..then is as valid in a sequence of machine instructions as it is in your everyday life. The way these laws are applied have not changed - only the tools that apply them have. Now there is that "maybe" fuzzy stuff? Regards.



#17170 A Software guy drowning in the Hardware world...

Posted by Bill E. on 27 August 2011 - 10:48 PM in General Discussion

Moskus, I actually did a double AND triple take on your posting title!! I had to laugh when I realized that I didn't get my title backwards!! Welcome to the world of "not just using stuff but making stuff as well". I am a professional Engineer (Electronic) and am fascinated every day by the really cool stuff out there today. A general comment on your dreams: I think you are biting off too much too early. The Netduino, or any C# capable device for that matter, is, in my opinion, not an entry-level approach. Have you thought about a more gentler way to get into the fight? Perhaps an Arduino or a Chipino? Sparkfun also has the T.I. "Launch" for $6 (which I bought). Learning about "interfacing" a microcontroller to the outside world is so much more easy and achievable (I believe) to grasp from the 8-bit C, or BASIC, realm. I have worked with the PIC family of microcontrollers for many years using PIC C compilers, PIC BASIC, even, ugghhh, assembly language. I do not consider myself to be the "master" by any means but I have not yet found a hardware challenge (within means, of course) that I couldn't solve with a PIC. Your X-10 stuff is a perfect example. The 3-axis analog output accelerometer is another. Don't let me disuade you! If you think you are ready then "get 'er done..." There are so many wonderful people (and some not so wonderful sadly) that are more than willing to help. I hope you have nothing but success. Regards.



#17169 A Hardware guy drowning in a Software world!

Posted by Bill E. on 27 August 2011 - 10:15 PM in General Discussion

I wanted to do one last reply on this post. This has indeed been a great post and I really appreciate the replies. I am attaching my design files and the hex file need to build my proximity (or collisioin) sensor. Good luck and don't hesitate to ask for help if you need it! Regards.

Attached Files




#17168 Help with Proper Servo Driving

Posted by Bill E. on 27 August 2011 - 10:06 PM in General Discussion

This reply has its roots in my post earlier about the Hardware guy having problems with the software side. I hope I can help out a little here. Let's see if I understand what you are after: you want to power a servo (a typical analog type), control it with a mini and power the mini from the same battery? All in all this is not so difficult but has its issues, as Mario clearly pointed out. Heat, heat, heat. You can power the mini right off of the 9V battery - no problem. The MC3392 regulator used on the mini can tolerate an absolute maximum of 20V so you have lots of headroom there. It will have some heat loss but it will be very little since the mini draws next to nothing in power. Now the servo is another matter. Some folks say, key word "say", that some servos can tolerate a 9V source for a short while. I would NOT recommend that. An elegant solution is to use a DC-DC converter like the one available at Digikey here: http://search.digike...1709-nd&stock=1 This device is over 90% effecient, needs no heatsink (no, or VERY LITTLE loss to heat) has a minimum input of 6.5V and has an output capable of up to 500ma. It is a drop-in replacement for the LM7805 part. And it is less than $8. I use these parts in my professional work. I love them. When I monitor the current supplied by my bench power supply and I stall a servo (not too easy to do!) I still draw less than 1/2A of current so the converter should do fine for your app. Another, more pricier one, is to use polymer-lithium batteries. For your app there woould be three in series (1.7V x 3 = 5.1V) for powering the mini off of pin 21 and your servo directly. If you use 4 in series (6.8V) you have enough overhead to power your mini via pin 24 and the servo off the same power source. That allows a small margin of isolation between the servo (very noisy electrically) and the mini. This would require a charger also. Check out Sparkfun. BTW, I ampowering my entire robot (3 servos, a mini on a Parallax Super Carrier) with 4 nickel-metal hydride batteries with no problem. That's only 4.8V. Hope this helps some. Regards.



#17076 A Hardware guy drowning in a Software world!

Posted by Bill E. on 26 August 2011 - 01:25 AM in General Discussion

What a great response so far. Thank you all. Glen, I ordered the book/downloaded/and started reading. Thanks for the link (I didn't know the ebook was ready yet!) and coupon. $12. Awesome. Coupon is still good ... Mario, I appreciate the warm welcome. I will keep your advice in mind. Stan4th, likewise - thanks for the support. Now Terry, I want to have interrupts in my code that will allow me to determine the time between interrupts of a simple photo reflective photodetector from both of the wheels (left & right). That way I can maintain a straight path and calculate turn angles. If you are familiar with the Parallax continuous rotating servos and the wheels they provide, there are 8 oval slots that can let the reflector "not refect" when the sensor is over a gap. That is my interrupt. Measure the time from the last gap to the current gap (for both left & right) and I have a reference. There is the need for my Timer questions. I am using (obsolete but replaceable with new RoHS parts) Fairchile QRB1134 sensors mounted close to the wheels to detect the gaps. There will be a gap every 45 degrees. The collision detector is a home made PIC based 38KHZ IR remote controller and an Osram IR LED. I pulse that at ~38KHZ and watch for reflections and the PIC processes all of that stuff for me. If anyone wants the schematic & HEX code for the detector just let me know. It works beautifully (and the parts are very inexpensive). I can provide jpg's if anyone wants. I am an EE. My degree is, believe it or not, in Computer Science!! But, that was in 1986. Soooo much has changed since then. I am the poster child of the "use it or lose it" syndrome. No-one wants to know about the low, sewer level details of the FAT system anymore. Or the gory details of a mere flip-flop ... Shall I continue? Great forum. Great posts. And, again, if anyone needs hardware help, I will keep my eyes open & try to help you.

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