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### Topic: Basic Ohms law problem (Read 8340 times)previous topic - next topic

#### kculm

#15
##### Feb 02, 2013, 04:58 pm
Wow, I am really impressed on all the input I got. This goes a long way to helping me learn.

Thanks  everyone.

#### kculm

#16
##### Feb 02, 2013, 05:01 pm

A diode would be better. Silicon diodes drop the voltage by about 0.7V when it passes through them. Two of them in series would drop it by 1.4V, etc.

Would I just put it inline with the Pos. side of the power?

#### retrolefty

#17
##### Feb 02, 2013, 05:07 pm

Wow, I am really impressed on all the input I got. This goes a long way to helping me learn.

Thanks  everyone.

The problem with that is you seem to be (or wanting to) learning basic electronics by memorizing a series of 'rules', rather then studying basic electronics DC theory which covers ohm's law and once completely understood would allow you to answer all those questions yourself once you are then ready to be introduced to semiconductors. Trying to learn by dealing with semiconductors (leds for example) and basic voltage/current/resistance at the same time is not a good way to start one's education into electronics, at least that is my opinion. There is a reason for the basic order of the subjects presented in learning electronics fundamentals and deviation from that is certainly an invitation for having gaps of understanding and substituting 'rules' for proper understanding of the principles and theory.

Lefty

#### JimboZA

#18
##### Feb 02, 2013, 05:39 pm
I'm giving serious consideration to buying the latest edition of Practical Electronics for Inventors for me and my daughter to share as we continue our electronics journey.

Johannesburg hams call me: ZS6JMB on Highveld rep 145.7875 (-600 & 88.5 tone)

#19
##### Feb 02, 2013, 07:11 pm
Or get a LDO regulator such as
http://www.digikey.com/product-detail/en/MC33269DT-5.0G/MC33269DT-5.0GOS-ND/1479179
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

#### kculm

#20
##### Feb 02, 2013, 08:23 pmLast Edit: Feb 02, 2013, 08:24 pm by kculm Reason: 1

The problem with that is you seem to be (or wanting to) learning basic electronics by memorizing a series of 'rules', rather then studying basic electronics DC

Lefty

Now that's that kind of Input I am looking for.  I have posted all over what would be the best way to get started in all this. I was not really getting any good input. Most would tell me to do the Arduion examples.
Even though that just shows me how to do things and not why.

I agree with you, I need to study the Basics first.

My issue is, I learn better by doing. I have found a few books on the subject but it's hard for me to retain unless I see it in action. That is way I have been doing some real odd ball projects.

If you have any recommendation on Books, I would be very grateful.

Thanks

#21

#### fungus

#23
##### Feb 02, 2013, 10:02 pm

A diode would be better. Silicon diodes drop the voltage by about 0.7V when it passes through them. Two of them in series would drop it by 1.4V, etc.

Would I just put it inline with the Pos. side of the power?

Yep.

#### dhenry

#24
##### Feb 02, 2013, 11:03 pmLast Edit: Feb 03, 2013, 12:40 am by Nick Gammon Reason: 1
Quote
Witch in reality puts out 6.24vdc and makes my scanner blink crazy.

If your arduino runs off an r/c oscillator, its frequency is more dependent on the voltage, but not that dependent.

AVRs can work comfortably at 6.24v. If you are really concerned about it, you can put a diode or an led in serial + a resistor to pull down the voltage.

Moderator edit: dhenry was banned for making this post. The quoted figure of 6.24V exceeds the maximum rating of the chip. This is not the first time that dhenry has made completely false assertions. Strikeout added by me. (Nick Gammon)

#### Grumpy_Mike

#25
##### Feb 02, 2013, 11:19 pm
Quote
AVRs can work comfortably at 6.24v.

Sure they can that is why the data sheet says
Quote
Maximum Operating Voltage ............................................ 6.0V

and then goes on to say
Quote
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent dam- age to the device. This is a stress rating only and functional operation of the device at these or other conditions beyond those indicated in the operational sections of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Oh but I forgot according to you data sheets are a conspiracy and only to be used if you are designing equipment for NASA

#### AWOL

#26
##### Feb 02, 2013, 11:23 pm
dhenry,
Stop posting arrant nonsense, or be banned.

Is that clear enough for you?

#### nickgammon

#27
##### Feb 02, 2013, 11:23 pm

AVRs can work comfortably at 6.24v. If you are really concerned about it, you can put a diode or an led in serial + a resistor to pull down the voltage.

dhenry, you keep telling people to read the datasheet, then just make stuff like this up.
Please post technical questions on the forum, not by personal message. Thanks!

#28
##### Feb 02, 2013, 11:40 pm
I'm  counting at least 4 moderators now that think dhenry be banned for this crap.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

#### retrolefty

#29
##### Feb 03, 2013, 12:27 am

I'm  counting at least 4 moderators now that think dhenry be banned for this crap.

I'm actually kind of surprised that because of how big this forum has become that there isn't a army of dhenry types, but he seems to be pretty unique among the membership around here.

But I will give dhenry this, he is like the relative that came to dinner but won't leave. I wonder what he gets out of posting here. Understanding his motivation might be a key to the puzzle that is dhenry. Or is that too flattering on him?

Just rambling I guess, go 49ers.

Lefty

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