As an old dummy, I would go to Goodwill or a junkyard and get a good looking old radio amplifier to salvage. IIRC, the volume control is a reasonable wattage wire wound variable resistor. It would also give you a box. The landfills are getting full of valuable, re-usable electronic components. Wayne Johnson wrote: > Just remember, 50% of the people are under average intelligence. > > If you really want to make a fancy battery tester, create one with a > microprocessor that runs the battery through various load levels, then > displays the resulting voltage as a graph on an LCD display. > > --- > Wayne Johnson, | There are two kinds of people: Those > | who say to God, "Thy will be done," > | and those to whom God says, "All right, > | then, have it your way." --C.S. Lewis > > > ------------------------------------------------------------------------ > *From:* Mike Miller <mbmiller+l at gmail.com> > *To:* TCLUG Mailing List <tclug-list at mn-linux.org> > *Sent:* Wednesday, May 15, 2019 11:01 PM > *Subject:* Re: [tclug-list] [OT] where to get a 100-ohm resistor? > > This is really helpful. It answered a bunch of questions I had but hadn't > asked. People were commenting on that YouTube battery-testing video that > a 100-ohm resister wouldn't be right for a D battery, but I guess it also > wouldn't be right for a 9-volt. > > Looking at more info out there on the web -- it's a problem for me that a > lot of people don't seem to know what they are doing, but they are still > there, teaching the world. ;-) > > Thanks again, Doug. > > Mike > > > On Sun, 12 May 2019, Doug Reed wrote: > >> Yes, the Ax-Man stores are the place to look if you don't want to ask >> someone to mail it to you. I believe there are 3 or 4 stores around >> town. The only stores I am familiar with are in St Paul and Fridley, but >> I thought there was one more in Bloomington. >> >> The color code for 100 ohms is brown-black-brown. But 100 ohms is too >> low for testing a 9V battery. 100 ohms is fine for testing 1.5 volt >> batteries at about 15 milliamp current load which is within the >> capability of all AAA or larger batteries. >> >> But 100 ohms will attempt to draw about 90 milliamps from a 9V battery. >> Most 9V batteries are rated for 50 milliamps maximum load. Your 100 ohm >> resistor will tend to suck them down so they all fail your test. For a >> similar test effect, you should use a 1000 ohm resistor, perhaps even >> higher, up to 3000 to 5000 ohms so the load is proportional to the >> battery capability. >> >> So when you are looking for the resistor at Ax-Man Surplus, the 100 ohm >> resistor should have Brown as the first band, black or brown or red for >> the second band, and Brown again for the third band. The bands are >> counted with the first band closest to one end. >> >> The 1000 ohm resistor would have the third band colored Red instead of >> brown. Since we don't care exactly what the value is between 1000 and >> 5000 ohms, the first band can be any of Brown or Red or Orange, or >> Yellow, and we don't care at all about the second band color. >> >> And I suggest that you look for a resistor that handles one-half watt >> dissipation or more. Your batteries should never approach that but the >> larger physical sizes are usually less likely to break from lots of >> handling. A half watt resistor is physically about 1/8" diameter and >> 1/2" long with leads about 1.5" on each end. >> >> The size you pick isn't really critical, it is really just for ease of >> handling. You will probably find multiple examples to choose from, I >> just suggest you don't choose the smallest size you find. Any resistor >> larger than 1/2 watt will also work of course, if that is what you find >> or want. The much larger watt values usually have the resistor value >> simply printed on the side. >> >> And of course buy more than one of each for when you break or loose one. >> :-) >> >> Good luck. If my description isn't enough to work from, you can easily >> find web pages that explain the resistor color code. And you can always >> bring your voltmeter to the store and use it to check the resistor value >> before you buy. Or buy a handful of different values that have brown or >> red on the third band and check them at home. No matter what you choose >> to do, the parts will probably cost less than the gas to get you to the >> store. >> >> Doug Reed. >> North St Paul. >> >> -- >> Scientists say the world is made up of protons, neutrons, and electrons. >> They forgot to mention MORONS. >> >> She had buried three husbands and at least two of them had already > been dead. > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > tclug-list at mn-linux.org <mailto:tclug-list at mn-linux.org> > http://mailman.mn-linux.org/mailman/listinfo/tclug-list > > > > > _______________________________________________ > TCLUG Mailing List - Minneapolis/St. Paul, Minnesota > tclug-list at mn-linux.org > http://mailman.mn-linux.org/mailman/listinfo/tclug-list >