### Author Topic: \$50 robot beginner question...  (Read 969 times)

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#### videk

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##### \$50 robot beginner question...
« on: July 17, 2012, 07:00:56 AM »
Hi, greetings from Poland and sorry for my English
I have a questions:
- I found that my voltage regulator (7805A) has about 2,5k resistance between the output and the ground. Is it means, that this regulator is bad and I should replace it (probably it was burnt when soldering )?

#### Soeren

• Supreme Robot
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##### Re: \$50 robot beginner question...
« Reply #1 on: July 17, 2012, 11:23:17 AM »
Hi,

- I found that my voltage regulator (7805A) has about 2,5k resistance between the output and the ground. Is it means, that this regulator is bad and I should replace it (probably it was burnt when soldering )?
How did you measure the 2.5k resistance (in circuit, chip alone or what?

The only way to test if a voltage regulator is OK, is to add a couple of capacitors (100..470nF from input terminal to ground terminal and around 22µF from output terminal to ground terminal) and test the output voltage at say 0.5A (eg. 10 Ohm, 3W resistor) and vary the input voltage between 8V and 10V while having a voltmeter over the output and ground terminals (in parallel with the load resistor).
You can't just put an Ohm-meter over its terminals like if it was a transistor.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

#### videk

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##### Re: \$50 robot beginner question...
« Reply #2 on: July 19, 2012, 04:26:36 AM »
Right. I checked this voltage regulator - it's OK. I did a connectivity test and i think everything works good. There is about 5.1V at sensor inputs and 4.8V (from my 4XAA baterry pack) at servo outputs. Now I will try to program my robot

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