Tips and Techniques

[sofaspud]

I enjoy reading Gerard Fonte's column in N&V, and his subject for June got me thinking that it might be nice to have a running thread here covering the same topic. So I'll try to start it off with something cheap and simple.<p>The type of coffee stirrers that are like two skinny straws stuck together make great LED standoffs. Cut them to whatever length you need.<p>If you can get ahold of two regular drinking straws with different diameters, with one that just fits inside of the other, you can use them for standoffs. Cut a piece from each straw that is the length you need, the straighter the cut the better. Place one piece inside of the other, which provides a little more sturdiness. Of course this tip isn't for heavy duty jobs, but for things like pcb standoffs it has worked great for me when I didn't have the exact-sized nylon standoffs on hand.

[Dean Huster]

To make it work, it has to be one of those threads that's "pasted" to the top of the forum. And you'll always get those, "Oh, brother. Everybody knows that. We've been doing that for years." They don't realize that there are folks new to the hobby that eat up tips and techniques.<p>"Tips & Techniques" used to be a regular column in the original Popular Electronics while QST had the similar "Hints & Kinks" column.<p>Here's a few more to keep this going:<p>Measuring High Resistance Values<p> Old vacuum tube voltmeters were capable of measuring up to 1000M ohms of resistance, although their accuracy wasn't the best. Although most service-type digital multimeters are very accurate, they are usually limited to a maximum of 20M ohms in the resistance measurement function. You can extend the range of the DMM for measuring much larger values. Locate a resistor, preferably a metal film type, with a value just under 20M ohms and accurately measure it with the DMM and label this value "Rp". Now, connect this resistor in parallel with the high-value resistor you wish to measure and note the new meter reading and label this value "Rt". The value of the unknown resistor can be calculated from these two readings where the unknown resistance, Rx = (RtRp)/(Rp-Rt). This reading will be nearly as accurate as the specified meter accuracy. If you perform a lot of these measurements, you can make a small jig that fits between your meter and your test leads with the Rp resistor soldered across the connectors. Measure Rp and mark this value on a label on the jig for later reference. Check the value of Rp annually and remark the label as necessary to account for aging of the resistor and/or recalibration of the multimeter.<p>
Shop Notebooks<p> During the years of tinkering that goes on with the hobby of electronics, new circuits are tried and repairs are made to odd household appliances. A lot of trivial information passes thorough your brain and several months or even years later, you'd like to recall that information. <p> I keep a pair of ring binders at close hand. One is a "scribble book", and is used for nearly everything. In it, I'll make disassembly drawings when taking apart complicated equipment for repair to insure that all the screws go back where they belong and that wires and connectors are returned to their proper location. If that equipment has a repair manual, I'll put the drawing with the manual. If there is no manual, the notebook can be the permanent place for the drawing. In five years when you have to repair the same item, the drawings are already at your disposal. Other times, I'll make quick drawings for power supplies or small amplifiers that I build and play with. I make no attempt at organizing this notebook. It's basically in chronological order.<p> Another ring binder is used just as often and has more order to it. It contains "factual" information. Just a few of the items it contains are a quick "cookbook" page of equations for designing monostable and astable 555 timer circuits; a page of equations for setting up the timing for all of the standard TTL and CMOS one-shots; a page of the 96 standard 1% resistor values; a page showing standard connections for stereo phone plugs and XLR connectors. These are things that you might find in other books, but that are used so often that having them in this notebook saves a lot of time redundant research. And you can add to them. For instance, in addition to the usual 555 timer equations, I have rearranged them to derive Ct or Ra or Rb given the other two values and frequency and include a nomograph for fast, ballpark values.<p>
Powered Computer Speakers<p> A small audio amplifier and speaker is often needed at the workbench when experimenting on various circuits. I find that a set of powered computer speakers can be installed out of the way and are perfect for most experiments. I've removed the 3.5mm phone connector from the input line and replaced it with a 3-pin square-pin connector for plugging directly into a solderless breadboard.<p>
Where the Rubber Meets the Road<p> Those lockable hemostats or forceps, more properly known as Kelly clamps, work fine for some applications, but they won't chow down on larger items and their light weight keeps you from using them to hold many items for soldering and other operations.<p> An old timer's trick is to wrap a few turns of a strong rubber band around the handles of your pliers, allowing them to hold objects without your mechanical input. The idea works for nearly any kind of pliers, whether long nose, needle nose, chain nose or combination. With the pliers rigged up this way, you can hold cables and connectors for soldering that would otherwise be too heavy or gangly for those medical clamps to be of much use. For even better weight-holding power, you can clamp one handle of the pliers in a small vise for fast and easy changes the subject being clamped. A source for the rubber band? Those small-diameter, wide and thick bands the grocer uses to hold broccoli stalks together are ideal and they have virtually no other use outside of their intended home around a vegetable.<p>
Saving Waste Solder<p> Many hobbyists desolder circuit boards for parts. At times, I've often had hundreds of boards that's I've salvaged for components, and the waste solder can accumulate into a sizeable stash. I never throw that old solder away, a fact I'm sure environmentalists appreciate. When I empty solder suckers, I dump the waste into a coffee can. Into that can also goes old lead wheel weights and other chunks of tin or lead. Periodically, I use a hotplate and propane torch to melt the contents of the can down into a smaller mass, skimming the dross of the surface.<p> This waste solder could be recycled commercially, but I use it for various things around the shop, mostly for lead weights. When I was younger, I used cut portions of my melted block to add weight to slot cars for added traction. Later in life, several pounds were added to the hanging weight used to hold down the loose roller chain used for raising my drill press table.<p>
More<p>I have about 30 of these tips and techniques on the computer that I was going to use either on a Website or in some kind of a publication. Some are simple like the rubber band tip and others are more complex and sophisticated.<p>
Dean

[philba]

I just finished reading the column and enjoyed it, too.<p>Sort of a tip. I find that external SCSI hard disk enclosures make nice project boxes. Often they have built in power supplies. I bought 5 LaCie boxes for $.50 each from a local surplus computer store. There is room for about a 6"x8" PCB (i.e. bigger than I'll likely ever make). The front is about 1.5" high by 7.5" wide. A little small but for $.50 I can live with it. The PSs were pretty nice - 5V at 1A and 12V at something similar. Both voltage levels are somewhat adjustable. Wish it had +/- 12V... it even have a little built in fan. Probably a couple 100 bucks new.

[sofaspud]

We're off to a good start I think. Dean, your notebook ideas remind me...
If you do any reverse-engineering for reasons like repair or hardware hacking, use the now-ubiquitous digital camera. Take a photo of each side of the circuit board. I load these on the computer and use a Paint-like program to mark off traces as I complete the schematic. It also allows me to view each side of the pcb at the same time, with less tedium than flipping the board over while keeping my bearings.

[Mike]

Dean,<p>I actually have a section on my website for tips and tricks at http://electronet.dyndns.org/electronet/tips.htm<p>If you are interested I can put them on there.

[MrAl]

Hello,<p>Couldnt help but reply to sofaspud's post...<p>I do the same thing only i use my scanner.
The scanner makes a nice high resolution pic
of both sides of the board (2 layers) then
i paste them side by side to examine both
sides 'at the same time'.
You could probably flip one and paste it
on top of the other too to see both layers of
copper runs as they really are connected if
you can get the contrast just right so as to
make the background look the same on each,
or possibly use a special color (like say red)
to fill in all the traces on one side then use
a program to remove all but that color (on
256 bit color images you could set the pallett
colors all to the same color except for that one
color which would remove everything else).<p>
Take care,
Al

[peter-f]

A sticky is like a posting evey day... this thread can surely generate that!<p>My notes are a bit more general
Dean- I like the notebook idea... but I put it on my computer...<p>digital notebook During an appliance repair, I pulled out the Digital camera and took a shot at each step of disassembly... then looked 'em over while reassembling... and filed the photos for future use.<p>project boxes I find a good source of numerous shapes and sizes (provided metal is NOT critical for your box) is a cigar store... cigar boxes are generally $1 each... in mahogany with hinges and latches!<p>power circuits A label in the breaker box is standard, but the list is generally incomplete, and you (should) always check twice when working on the wiring... So my house has the Ckt# on the list... and behind the switch plate or outlet cover.<p>urethane glue has a short shelf life once the bottle is open (cures on exposure to water vapor). So I store mine with air squeezed out... and dispenser end Down... so any cured 'skin' is away from the business end of the bottle.<p>That'll be all today.<p>[ May 22, 2005: Message edited by: peter-f ]</p>

[Dean Huster]

Sofaspud, I like the digital camera idea for recording the process. Remember that I'm older and my technology tends to lean toward 1964.<p>Al, I've used the scanner idea before and it has better results than trying to use a copier for it seems to have much better depth of field and plays with the colors better.<p>Peter, you had some good ones there. My problem with the "digital notebook" is the fact that I can do it a lot faster with the mean and dirty drawings on college-ruled paper. And the paper version is a lot easier to leaf through to find stuff. Now, scanning the paper pages and backing them up on the computer might be a good way to go, too!<p>Regarding your breaker box idea: The first thing I always did when moving into a "new" home was to make a detailed list for the breaker box. One list did a room-by-room listing of every receptacle, light and permanent appliance (e.g., smoke detector, HVAC, water heater) and the breaker that's assigned to is. A second list reorganizes that into a list of these items controlled by each specific breaker. One list tells you which breaker to kill for working on the front porch light, the other tells you what all that breaker will douse while you're working.<p>And to add to your urethane glue item. When you first open the bottle and use it for the first time, never, ever let sides go so that you suck air back in. Push out the glue you need and put the cap back on before releasing the bottle. Keeps ingested water vapor to a minimum.<p>In a similar vein, I don't always go through a caulking tube of silicone at one time. I cut the tip off enough so that I can insert (by wiggling the head around a little) a 6d box nail head-first into the end. That way, I can pull the cured plug out next time I want to use the tube. Snap-on caps just don't do the job.<p>Dean

[Donald S. Lambert]

AA BATTERIES
A hint to keep them under control when you need to take spare batteries with youi for you camera or radio or whatever.
A soft plastic cassette case (some call them mailing cases) will hold 9 AA batteries, Nicad or regular, and keep them in one place. You will need to put a couple of rubber bands around the case to keep it closed since the batteries are just a little bit thicker than a cassette. The two tbs that originally were to keep the tape from getting loose need to be broken out. If the tabs pull a little of the bottom of the case out leaving a hole that still is OK since a battery won't fall out. The cassette case can be used for AAA batteries but don't hold them as securely in place. A piece of tape will enable you to mark the used ones so you don't put that back in again for a fresh one.
Greybie

[sofaspud]

probe tips
pun intended, spelling and grammar errors not<p>I have a couple of straight pins stuck into the padding inside my meter case. (These even have red & black round plastic heads.) Combined with alligator clip meter leads, they come in handy for those rare times I need insulation-piercing test leads. In a pinch, they work well for surface-mount parts also.<p>I've been stabbed by my regular SMT probes too many times. OUCH! I saved some foam that ships with through-hole ICs and now protect myself and the probe tips by keeping them stuck into the foam.<p>If interested in making homemade probes, you may have noticed many project parts lists suggest nails, air pump needle valves, or nuts and bolts with ends ground to a point. None of those options have ever appealed to me. I've found 1-7/8" needles from the leathercrafts department of the local Hobby Lobby make excellent probe tips (about $2 for a package of 10). The eye is conveniently soldered into the circuit. The needle goes through the hole in the enclosure and is then held firmly in place with heatshrink tubing, or a short piece of insulation saved from stripped wire, which is slid up the needle and against the enclosure.<p>[ May 23, 2005: Message edited by: sofaspud ]</p>

[Dave Dixon]

WIRE CUTTER LEAD RETAINER
I may have shared this before. While holding my wirecutters (dikes) closed with a rubber band, fill the recessed area with silicon (RTV) and let cure. Then slice between the blades with a razor blade. When using these to cut leads, the leads don't fly across the room, or into the project area and stay with the tool until you release. I did this at least two years ago, and the silicon is still in good shape.
Dave

[peter-f]

Another:
Battery use - I find I can go through plenty of AA batteries - and that my remote controls do NOT need fresh ones to work well... so batteries get cycled from walkman/radio/camera to the remotes after the motors and amps no longer get sufficient power.<p>(but thrn, EE's would know that)

[jollyrgr]

Other hints:<p>Score a radius cut (not very deep!) on rolls of electrical tape. It makes tearing off a piece of tape easier.<p>Before AOL wised up and started sending CDs in cardboard mailers I reused the plastic "clam shell" DVD mailers to store the "Dollar Deals" DVDs (the ones that come in a cardboard envelope).<p>Old medicine bottles make excellent holders for small screws or other hardware.<p>Plain old bar soap is great for putting on wood screws. It makes driving them in much easier.<p>Putting a strong magnet on the shaft of a screw driver makes it easier to start a screw in a recessed area. Alternately the screw can be rubbed on a magnet several times (in the same direction) to make the screw magnetic.<p>Petroleum jelly makes a nice coating on exposed electrical connections (like car battery terminals) and is non toxic and cheap.

[Enzo]

Oooooooh I love shop tips. I used to write a shop column in a trade mag myself. I am working on a book - who isn't - and have a spiral notebook next to me at all times. It is ful of such stuff.<p>The one tip I have gotten the most feedback over the years is this:<p>When reinstalling sheetmetal or wood screws, drop them into the hole and rotate them backwards until they drop into the old threads. Then turn them on in. Otherwise you cut new threads each time, and it only takes a few times to run out of threads.<p>Also<p>Stripped wood hole? drip some glue into the hole, then poke hardwood toothpicks into the hole and break them off at the surface. The hole full of hardwood offers fresh thread material.<p>Medicine bottles are great for small parts, but if you are in good health, get empty 35mm film cans from a photo developer. Hurry while there still ARE photo developers.<p>Speakers can be tested for rubbing voice coils be holding them by the frame in from of you face outwards, then whacking the back of the magnet with your balled fist. You can also be official and use a rubber mallet, but what's the fun of that? You will hear the flapping sound of a rubbing voice coil easily.<p>If there are plastic connectors where wires connect to circuit boards, mark them with various numbers of lines or color in one side to help you know where they belong at reassembly.<p>Often the magnet of a speaker is a handy place to park screws.<p>Use your nose. Burnt resistors, transistors, hot metal, and other things smell different. And you old timers will never forget the smell of a burnt selenium rectifier as long as you live. It helps determine what burnt up.<p>Buy a Dremel tool.<p>If the head of a phillips screw strips, use a cutoff wheel in the dremel - or a hand drill - to saw a straight slot across the screw head. Then turn it out with a flat blade driver.<p>In audio circuits, 60Hz hum comes from grounding or shielding problems, while 120Hz hum comes from power supply ripple. Learn to recognize the difference by ear.<p>If there is a crack growing across a pc board, drill a small hole through the board at the end of the crack as a strain relief to prevent further growth. Car windshield guys know this trick.<p>An old VCR - or other asian made consumer electronic thing - is a handy source of metric hardware. Before an old VCR hits the trash, I take the AC cord and the screws.<p>I also keep a three ring binder of useful info. My bench is for pro audio. But I also include a chart of small light bulb types and rating, and a chart with fraction/decimal/metric equivalents.

[Dean Huster]

Remember in the "old" days, Enzo, 35mm film came in aluminum cans with screw-on lids with a rubber gasket built in. Nice for little cable-end electronics projects, but they're disappearing faster than the plastic ones, of course.<p>These days, VCRs, DVD players, CD players, pagers, cellular phones, computer boards ... not only are they a source of metric hardware, they're a source of general-purposd SMD components. I have yet to buy any SMD but have a pretty good collection from harvesting the parts from the old Asian goods.<p>Broken and Cheap Tools<p> I never throw away a broken tool and keep on hand a lot of cheap import tools. Even though a screwdriver may no longer be useful as such, I can grind it down or solder additions onto it to convert it into a specialized tool for one-time or infrequent use. I have several nutdrivers and screwdrivers that are now spanner wrenches and Allen wrenches that have been converted into fine-tipped center punches or in-between size Allens for worn or odd setscrew sizes. Other screwdrivers have become scribes while others have had male BNC connector collars soldered to them to keep female BNC connectors from rotating in round holes while attaching mounting nuts. Other screwdrivers have had 3/8" hex wrench rings brazed or MIG welded to them to loosen or tighten "F" connectors, especially if they're in tight places.<p> I've been known to modify otherwise new and high-end tools for specialty use. I've ground down Craftsman offset box-end wrenches for thin, shallow heads so that they would fit into tight spaces for removing the BNC mounting nuts in Tektronix test equipment. Another Craftsman 5/8" deep-well hex socket had the opening ground to a thin profile so that it could fit on a crowded front panel for removing specialized connector mounting nuts. <p>
Reel Good Idea<p>Would you like to see all of those AOL and other "freebie" CDs put to practical use? Cut a short length (whatever width you need) of 1" or 1.5" diameter PVC pipe, sand both ends smooth and parallel to each other, center and attach a discarded CD to both ends with epoxy, drill the appropriate holes in the hub and you have a reel for storing wire, string, heat-shrinkable tubing, braid, bath tub chain, ribbon, rick-rack, seam binding, small hose, sewing trim, cable lacing, sausage casings ... you name it. Slip them on a steel rod, small pipe or dowel rod (1 / 2 - inch outside diameter) to gang up a lot of reels. Add one of those mini-CDs between each reel if necessary to act as a washer to help keep adjacent reels from spinning. Make a short axle from a bolt, metal washers, rubber washers and a nut to chuck into a drill for winding long lengths of material onto the reels.<p>Now that you've seen how to make them, you can get an idea of where to drill the holes in the hubs and the flanges BEFORE you assemble the reel to make drilling easier. Traditional reels have one hole in the hub alongside a flange that goes through to the inside of the hub. A second hole is in the flange adjacent to the hub hole. Two more holes are near the outer perimeter of each flange as a place to poke the free end of wire so that it doesn't unravel from the reel.<p>Creating Large Currents<p> There are times when you need to produce currents that are far beyond what your bench power supply or function generator can produce. One instance of this is when you must check the accuracy of a high-current clamp-on current probe. Another might be for a science demonstration where you must pass several hundred amps through a heavy wire to show how the magnetic field affects a compass. In either case, you don't need a source capable of high current output.<p> Consider the current probe example. If you need 10 amps of alternating current at a frequency of 1KHz, and your function generator can output at least 100 milliamps, you can wind a small coil of 100 turns of small-gauge varnished magnet wire into a four-inch loop. If wound carefully around a form with attention to keeping the overall diameter so that the current probe can fit around it, you can use shellac to hold the finished turns in place. Use a small-value resistor in series with the loop on the ground side of the function generator to monitor the voltage and adjust the generator output until you have a voltage equal to the value of the resistor multiplied by 100 milliamps. At that point, you will have 100 milliamps flowing in each turn of the coil and each loop will contribute 100ma for a total of 10 amps for all 100 turns.<p> The same can be done for the science demonstration. If you need 500 amps of direct current, you can obtain enough magnet wire or small-gauge plastic insulated wire to make 100 turns. 5 amps flowing through this coil from a power supply will produce the equivalent of 500 amps of current through all 100 turns combined. If you use 500 turns, you only need one amp of current from your supply.<p>Bulb-type Solder Suckers<p>There are some bulb-type solder suckers that work well for small desoldering jobs, but the waste solder accumulates in the bulb. The opening to the bulb is like a fish trap – the solder can go in but won't easily come out. I cut a hole in the opposite end of the bulb and inserted the neck of an old pill bottle after removing the snap off lid. If the hole is cut correctly, the bottle fits snugly, keeping the suction high and after a fair amount of use, I can invert the bulb, shake it up and down a little and collect the waste solder in the bottle. I then remove it, dump the solder into my scrap solder can, put the bottle back in place and I'm ready to go again.<p>
Finding the Right Circuit Breaker<p>Often one must do some electrical work in the home and the first thing you must do is turn off the circuit breaker or unscrew the fuse that powers the circuit that's been targeted. But when the service panel is far from the business end of the circuit, it's nearly impossible to know which breaker to kill if you don't already know which breakers control the various circuits. Even a buddy often can't yell loud enough for you to hear if you've killed the correct breaker.<p>If you put a wireless baby monitor transmitter or a walkie-talkie that you can hold in the "transmit" function next to a line-powered radio that's plugged into the circuit in question, you can take the monitor receiver with you to the service panel and flip breakers until you no longer hear the radio in the monitor receiver. Then a double check with a voltmeter at the outlet will assure you that power has been properly cut off to that circuit.<p>
Dean