# Help on a few questions.

Discussion in 'Homework Help' started by Court, Jul 30, 2014.

1. ### Court Thread Starter New Member

Jul 30, 2014
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0
I have an important job interview and they will be quizzing me on these questions. I have a degree in electronics but its been years since I have done this. I have a great opportunity and need a little help. Any and all help is appreciated. There are 10 questions that I could be asked. I have attached them.

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2. ### shteii01 AAC Fanatic!

Feb 19, 2010
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Did someone finally turn off google?

3. ### Court Thread Starter New Member

Jul 30, 2014
6
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I am looking for some real time help. I have googled a few things. I thought maybe I could get some better understanding than reading through pages and pages.

4. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,500
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The last page is up side down.

5. ### tshuck Well-Known Member

Oct 18, 2012
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Which, in particular, do you need help with?

6. ### Court Thread Starter New Member

Jul 30, 2014
6
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Right side up now!

7. ### Court Thread Starter New Member

Jul 30, 2014
6
0
I mainly need help with the schematics. I have an idea of the output for the op amp. The solenoid driver I have really no idea. I have been going through my old school books and can't find anything about it.

8. ### tshuck Well-Known Member

Oct 18, 2012
3,531
675
Question 8 seems a bit unclear, but, you can at least get the input voltage required for a 50% duty cycle using linear interpolation on the two points you are given.

Use: y – y1 = m(x – x1), where (x,y) and (x1,y1) are your given data points.

9. ### Court Thread Starter New Member

Jul 30, 2014
6
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Really you lost me.

10. ### shteii01 AAC Fanatic!

Feb 19, 2010
3,500
511

When voltage at Pin 3 is 3 volts, duty cycle is 30%.
When voltage at Pin 3 is 2.6 volts, the duty cycle is 40%.
So.
A reduction of voltage at Pin 3 by 0.4 volts produced an increase in duty cycle by 10%.
You need duty cycle of 50%. To me it seems that if I reduced the voltage at Pin 3 by another 0.4 volts, I would gain another 10% in the duty cycle. So. When voltage at Pin 3 is 2.2 volts, the duty cycle will be 50%. That is why they stuck the adjustable resistor at Pin 3, so that you can decrease the the voltage drop at Pin 3 and increase the duty cycle.
And.
Based on the two points that the note provided, you can derive the linear relationship between the voltage drop at Pin 3 and the length of the duty cycle.
y=mx+b
Duty Cycle=m*Pin 3 voltage+b
30%=m*3+b
40%=m*2.6+b
Can you do this middle school math and find slope m and y intercept b?

11. ### Court Thread Starter New Member

Jul 30, 2014
6
0
Yes thank you. I guess I need glasses.