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Author Topic: Schematic  (Read 2514 times)

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Offline RadikenTopic starter

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Schematic
« on: May 23, 2007, 12:07:35 AM »
I'm sorry to bug everyone with another schematic, but I had to scrap the first one and redesign...

This one uses the OOPic version of the PIC16F877 chip.
I decided to switch because I had the OOPic chip already, as with the eeprom needed too...

Just one question:
Do I really need I/O ports with regulated voltage? I can't really think of a sensor that couldn't just be plugged into the analog in...

Any thoughts are appreciated!
Thanks!

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Offline Ro-Bot-X

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Re: Schematic
« Reply #1 on: May 23, 2007, 09:38:59 AM »
Use regulated power supply for all sensors.

I have the OOPIC-R board. On this board they divided the I/O pins in groups of 5. Each group's power line goes to a jumper from which the user can select either 5v or unregulated. Why don't you do just that?

I use this board to control an arm with 6 servos, the pan and tilt head (2 servos), a PING ultrasonic sensor, an Eltec pyro sensor and an IR sensor for the gripper. I have grouped the devices like this: US sensor, Eltec sensor, IR sensor and the 2 servos for the head on the first group, powered with 5v. All the other servos (for the arm) are powered from the 6V battery (unregulated). So you see, you can have both ways with just a jumper.
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Offline Admin

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Re: Schematic
« Reply #2 on: May 23, 2007, 10:05:57 AM »
Quote
Use regulated power supply for all sensors.
Its cause sensors give out different readings depending upon input voltage.

Offline RadikenTopic starter

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Re: Schematic
« Reply #3 on: May 23, 2007, 10:51:03 AM »
I think there was some confusion...
The I/O lines are strictly for servos, and any sensor that I need to plug in can go to one of the analog in ports...

Although,
Ro-Bot-X, your jumper statement sounds pretty useful, I think I'll go with that...
« Last Edit: May 23, 2007, 10:54:25 AM by Radiken »
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Offline Admin

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Re: Schematic
« Reply #4 on: May 23, 2007, 10:54:12 AM »
Quote
any sensor that I need to plug in can go to one of the analog in ports...
but all sensors need power and ground to work . . . the analog pin is for output, not powering the sensor ;D

since you need to regulate voltage to your microcontroller anyway, just use that voltage . . .

Offline RadikenTopic starter

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Re: Schematic
« Reply #5 on: May 23, 2007, 11:38:54 AM »
That is what I already have set up on the schematic... right?


The top ports I made are for analog input. Ground is on the left, regulated power in the middle, and inputs to the IC on the right...

The bottom ports are unregulated V. ports for servos. Same pin setup as the analog inputs...

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Offline RadikenTopic starter

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Re: Schematic
« Reply #6 on: May 23, 2007, 12:09:13 PM »
In the datasheet for the eeprom, it says that WP could be connected to VDD, VSS, of left standing...
Which would be the best option?

(the eeprom on the schematic isn't the right one... I'm actually using the 24LC256)
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Offline rgcustodio

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Re: Schematic
« Reply #7 on: May 25, 2007, 11:24:44 AM »
I'm also playing with the same chip. The answer lies in the data sheet :)

"2.4 Write-Protect (WP)
This pin must be connected to either VSS or VCC. If tied to VSS, write operations are enabled. If tied to VCC, write operations are inhibited but read operations are not affected."

If you'll have read-only data written to the EEPROM once (and only once), then maybe wiring WP to Vcc would be a good idea so that no one accidentally overwrites the data you stored. If you're gonna be accessing the EEPROM like SRAM, ie storage of random bits and bytes for path, or temporary sensor data, you can connect it to Vss so that you the EEPROM will be R/W.

You should also note that the EEPROM is good only for a million erase/write cycles. Read operations does not affect this count. (All according to the data sheet.)
« Last Edit: May 25, 2007, 11:32:55 AM by rgcustodio »
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