Search found 106 matches

by ecerfoglio
Mon Mar 19, 2007 8:35 am
Forum: General Discussion
Topic: Difference between a Crystal, Oscillator, and Resonator
Replies: 6
Views: 1734

they have a three-pin crystal shown, but I have not been able to find one. All the crystals seem to be two-pin. It's common to use a two pin crystal with its case soldered to ground, to provide both shielding (against EMI generation) and mechanical support (against external vibration). That may be ...
by ecerfoglio
Thu Mar 15, 2007 2:04 pm
Forum: General Discussion
Topic: Question about resistor tolerances
Replies: 31
Views: 5309

Yes, you may use a 9V battery as shown in your drawing. When you say "split supply", do you mean two totally different power sources? Yes, they may be two different power sources (in series) or a single supply with two outputs and three wires: >> +V (positive with respect to ground), >> Ground or co...
by ecerfoglio
Wed Mar 14, 2007 11:48 am
Forum: General Discussion
Topic: Question about resistor tolerances
Replies: 31
Views: 5309

Does this tolerance come into affect while the circuit is in use (temperature change), ..... Yes, you "should" measure the resistor at all the temperatures it may have when working (or at least at the lowest and highest expected temperatures) to be able to say that it stays within 1% of the nominal...
by ecerfoglio
Tue Mar 06, 2007 7:05 am
Forum: General Discussion
Topic: AA Batteries are corroding!
Replies: 13
Views: 2389

As others have stated you must clean the old corrosion out. Baking soda and warm water is excellent. I clean my car batteries with this mixture probably once a year or maybe once every other year. An old toothbrush works well for this type of job. Baking soda is an alkali, usefull for cleaning an a...
by ecerfoglio
Mon Feb 05, 2007 10:18 am
Forum: General Discussion
Topic: Sensor used for temperature regulating soldering irons?
Replies: 11
Views: 2352

Thermistors, diodes, etc are all semiconductors and have a (relatively) low temperature limit. You should use a sensor that is made of metal: either a thermocuple or a wire resistor . If you use some form of PWM or (phase angle) to control the iron's temperature, you may even use the heater's own re...
by ecerfoglio
Wed Jan 31, 2007 12:55 pm
Forum: General Discussion
Topic: Shielding Generator
Replies: 15
Views: 5827

Stainless steel (which is high in nickel) seems to be a pretty good shield for both magnetic (magnets don't stick to it) and electric fields (its conductive). (haklesup) Non magnetic materials do not shield magnetic fields. You need a magnetic material. In fact, some submersible deep well pumps are...
by ecerfoglio
Mon Jan 29, 2007 11:14 am
Forum: General Discussion
Topic: Current Indicator Circuit Breaker
Replies: 14
Views: 3812

Do you know what formula applies for current transformers? For 1 Ampere AC to yield 1 Volt AC, how many turns are needed (Externet) Current transformers are just that: Current transformers . :shock:. You obtain current, not voltage. If you have a turns ratio of, say, 25 to 1, and you have 25 ampere...
by ecerfoglio
Wed Jan 17, 2007 1:50 pm
Forum: General Discussion
Topic: Current Indicator Circuit Breaker
Replies: 14
Views: 3812

You may order a bigger pannel with some extra space, and place a current transformer on each output circuit. I don't know if they make current transformers in the format of the american breakers, but I've seen them built to fit in the european "DIN" format. (Here in Argentina we use mostly DIN forma...
by ecerfoglio
Wed Jan 17, 2007 9:34 am
Forum: General Discussion
Topic: Monitoring Water Current direction and speed
Replies: 19
Views: 7830

Before you start remember a single line will spin like a prop, not allowing you to have a set "direction", only a flow? (Chris) Or you may use an "hidrodinamic" buoy, shaped so it allways lines up with the current. Then if you place a compass (electronic) inside de buoy you may log the buoy's orien...
by ecerfoglio
Fri Jan 12, 2007 9:41 am
Forum: General Discussion
Topic: Motors as Generators
Replies: 21
Views: 5228

To use a DC permanent magnet motor as a generator you just spin its axle and it works. If you have a (DC) motor with a field winding you have to use an external supply to excite it or "flash" to set up some residual magnetism in the field coil laminations and then use part of the generated current t...
by ecerfoglio
Fri Dec 29, 2006 5:56 am
Forum: General Discussion
Topic: Electrolytic capacitors in series...
Replies: 20
Views: 5350

You may use a zenner diode (instead of a resistor) in paralell with each capacitor to act as a safety limit. Choose zenner with a voltage that is slightly less that the capacitor's maximum rating. Add a current limiting resistor between the caps/zenners series and the power supply (the car's electri...
by ecerfoglio
Fri Dec 01, 2006 6:27 am
Forum: General Discussion
Topic: 4050 Non Inverting Hex Buffer
Replies: 7
Views: 1986

Looking at the datasheet ( http://www.fairchildsemi.com/ds/CD%2FCD4049UBC.pdf ), the 4050's output can sink 5 mA and source 1.6 mA (typical values @ 25°C). Its max. input current is 1 microA, which gives a DC fanout of :shock: :shock: over 1600 driven devices :shock: :shock: Of course, AC fanout is...
by ecerfoglio
Thu Nov 30, 2006 9:25 am
Forum: General Discussion
Topic: Drill bit sharpening...
Replies: 16
Views: 3408

Widia cutting tips are used in "industrial" machines like lathes. The cutting edge is shaped like their steel counterparts (ussually with an angle of about 70°) They remain sharp longer, allowing more time between sharpenings. But they are more fragile than steel, and may break if you drop or hit t...
by ecerfoglio
Thu Nov 23, 2006 6:43 am
Forum: General Discussion
Topic: Permanent magnet and field wound motors...
Replies: 1
Views: 726

does a permanent magnet motor uses less power to achieve the same work as an equal wound one because uses no extra electricity to make the field YES, the DC motor converts to mechanical work only part of the power that goes into it's armature winding (converted power = armature current x back EMF)....
by ecerfoglio
Thu Nov 16, 2006 5:12 am
Forum: General Discussion
Topic: 555 timer headaches!
Replies: 31
Views: 6351

I would tie reset high (pin 4). Also, couple CV (pin 5) to gnd. (Philba) Good advice. Also add plenty of power suply bypassing near the IC (at least one 100n = .1 micro between pins 1 (gnd) and 8 (+V)) Without the "extra" resistor, when the discharge transistor turns on there is a *large* current t...