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1021  Using Arduino / General Electronics / Re: Testing a Voltage Regulator on: February 08, 2013, 12:42:05 pm
You can damage the NI-MH or CD packs by totally discharging them and leaving them in that state for very long. Small nickel crystals form and poke between the separator shorting the cell out. This doesn't happen except when the cell is completely discharged and is the major cause of cell failure.
Use a battery monitor of some kind and remember that it too draws current.

1022  Using Arduino / General Electronics / Re: what the flux? on: February 08, 2013, 12:27:49 pm
If you use a water soluble flux cleaning is easy. 1. Lather, 2. rise, 3. Repeat...
If not and you use a solvent containing water (AKA Alcohol) you must wait until or dry the PCB first, A heat gun works very well.
{Edit RKJ}
AS MarkT pointed out above orange oil is the best solvent for that purpose.

1023  Using Arduino / General Electronics / Re: Designing optocoupler circuit for arduino input on: February 08, 2013, 12:21:17 pm
That is not a great idea... it looks good on paper BUT Line transients can kill the opto, I've tried it and every easy protection method with very little success. Over time Every opto-isolator I used died. The trick to success is to use a neon light and an LDR shielded from ambient light. For 230 V mains power I would use a 220K  series resistor and an NE2H neon light to control an LDR.

1024  Using Arduino / General Electronics / Re: Limited analog inputs (multiplexing?) on: February 08, 2013, 12:10:25 pm
A plain old CD4066 would give 2 channels with one control connection. Use one of the gates as an inverter and you have a 1 wire 2 input analog switch, I would however use voltage followers to drive the transmission  gates as they do have a small dc resistance. This is a "Best Practices" kind of engineering thing, Or If you do that you will have less trouble later and it provides a layer of protection for the processor.

1025  Using Arduino / General Electronics / Re: How Are Masters and Slaves designated in I2C and SPI connections? on: February 08, 2013, 11:57:35 am
I read that link and..
I Think This phrase is incorrect
iIf powering the Arduinos independently is an issue, connect the 5V output of the Master Arduino to the VIN pin on the slave.
As the Vin porrt is the input to the regulator and would underpower the second Arduino by the inherent I/O differential of the second regulator because of the 5V source, The sentence should read:
If powering the Arduinos independently is an issue, connect the VIN Pin on the  Master Arduino to the VIN pin on the slave.
This will work without issue.. as long as you remember to "Connect the Grounds".

1026  Using Arduino / General Electronics / Re: Testing a Voltage Regulator on: February 08, 2013, 11:28:11 am
Measuring battery voltage under charge can be misleading.. The voltage at the terminals Must be higher than the nominal battery voltage to charge it, It's called the forcing function and is used to determine the battery condition under charge.. If you know approximately the battery charge then a comparison of the voltage or current at several places during the charge cycle can flag a failing battery early and is a common technique to monitor and return those values to the controller to indicate apparent battery charge warning conditions early. Very commonly used to report battery conditions in un-monitored remote control points.

1027  Using Arduino / General Electronics / Re: Schmitt Trigger Oscillators?! on: February 08, 2013, 11:12:31 am
That circuit is so very handy.. so many uses for it and when you disconnect the feedback makes a great input conditioner for any type of mechanical switch... Add a couple more gates and make a mic preamp for an electret microphone... Makes a great noise sensor with a pot for threshold setting. With 40 DB of linear gain. (CD4069UB only).

1028  Using Arduino / General Electronics / Re: PWM to reduce relay coil current consumption on: February 08, 2013, 10:57:57 am
Pull in and hold voltages can be found in most relay catalogs. It is a common trick to add a capacitor across the base input resistor.. The pulse leading edge is enough to "Pick Up" the relay and the DC through the base resistor is what keeps the relay pulled in and at a lower value than the initial pulse. Much easier than PWM as you only need to know the approximate Beta of the relay driver to calculate the resistor value necessary for the reduced current "Holding Current" or voltage from the catalog. It is also much easier on the power supply... and there are no issues with the relay "Singing" or resonating at the PWM frequency...

1029  Using Arduino / General Electronics / Re: I learned a new word today... on: February 08, 2013, 10:37:45 am
Some people get it and some don't... Thank you Jim for the information.. I wondered why it was orange...!

1030  Using Arduino / General Electronics / Re: Schmitt Trigger Oscillators?! on: February 08, 2013, 10:33:48 am
No just the right chip, your choice of the HC14 was the error, easily fixed, either use 3 gates of a 74HC14 or  1 gate from a CD40106 or a CD4584. You can also use a CD4093 if you tie the inputs together or use one input to gate the oscillator, which is a better option than my suggestion above because there is no startup delay as there is with the diode gate, I've used both many times on many different configurations. Once I set one up driving the gate of a BIG mosfet which switched 12 v to an ignitiion coil and a spark gap that was coupled to a 75 cm ring of 10 Ga copper wire and a 100 PF cap @ 10 KV... Made a great noise source to do a rough noise immunity test. When I initially tested it... It destroyed 3 calculators I had on my bench... About 100 watts of power @ ~  50 MHz... in 2 hours... From scratch.. @50 MHz. Note: The device was an AM transmitter making power @ 50 MHz modulated by the 2KHz signal from the Cmos gates...

1031  Using Arduino / General Electronics / Re: Schmitt Trigger Oscillators?! on: February 08, 2013, 09:26:08 am
Go find a copy of Donald Lancasters book Cmos Cookbook.. The information is there. There is a whole chapter devoted to this most handy little circuit and it's many variations.
Your likely issue is not enough gain in the gate package. The 'HC14 takes 3 sections,, It doesn't work well with one.
What IC are you using for the gate? a 74CH14? try a CD4069UB or a CD40106 (CD4584?) I've used both..
An interesting circuit the gates need an inversion to work so it is necessary to use 1, 3, 5... always an odd number. This circuit is most often used as an oscillator for an led used a blinking annunciator.. as it can be gated with a diode, cathode to the gate (for a dual package use the C. When the input is low the oscillator will run when high it will stop. Very handy sort of electronic glue for the designer. These are typically implemented... when the designer has run out of other options to blink a light or beep a sounder. The circuit also makes a good oscillator for resonators and 'some' crystals too, With a 4069UB the device has been successfully used ad a linear amplifier for small microphones... Too.

1032  Using Arduino / Programming Questions / Re: how would i code this on: February 07, 2013, 10:27:26 pm
Personally I like my curly's Right to the Wall. The Left wall that is...
1033  Using Arduino / Programming Questions / Re: how would i code this on: February 07, 2013, 10:08:27 pm
You Mr Crossroads, set a poor example... OTOH If he wrote code like I write letters.. No one could read it..

1034  Using Arduino / Displays / Re: kingbright double 7-segment with dp missing (?) on: February 05, 2013, 04:49:23 pm
Production is much easier... You only build one version.. Cheaper too, the base price covers the cost of the parts for any configuration so the device is always paid for fully.

1035  Using Arduino / General Electronics / Re: Circuitry. on: February 04, 2013, 03:17:50 am
Don't forget the limited 2.7 to 3.8 Volt Vcc range as well. The battery can be also be a 100F super cap if you have room on your BOM, just consult the spec sheet before powering it down, you might have issues.
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