PR23 won't work without some components?

[altan]

Hi gurus,

I have read through the schematics and the manual for PR23. By referring to the schematic, I have already soldered the components for the voltage regulator circuit, the UIC programmer, the 3 switches, microcontroller and the buzzer. I would like to know if I can run the microcontroller without the motor driver, and line sensing comparator components?

I already loaded the hex file into the PIC microcontroller using the UIC00B programmer without those components and it did not have any problem.

The problem I have is there is no beep when I turn it on and the LCD just show a row of box. Is it because I did not solder the other components or is my PIC chip faulty?

The reason I didn't solder all components because I was checking each circuit before I finish the whole robot. I solder the components in this order -> voltage regulator (LED got light when on) -> switches (all working, tested with voltmeter) -> buzzer (got sound when 5v was applied) -> microcontroller with UIC (can write with PICkit 2)-> LCD module (got a row of box).

I tried writing, erasing, read, and blank check but still no response from the LCD or the buzzer.

What should I do next? Thanks in advance.

Here is the picture of the PR23...

[ober]

How about the Crystal for the microcontroller? It should be underneath the PIC, of course the capacitors for it too, should be 30pF cap.

Do also check whether there is 5V supply to PIC from voltage regulator.

[altan]

Yes, I already soldered the crystal, three 0.1 capacitor and the two 30 pf capacitors under the microcontroller. Before I soldered the microcontroller components, I soldered the 40 pin holder first and tested both VCC pin with the multimeter (got about 5 v) and I tested the buzzer by hot wiring the VCC pin with the RE2 pin (on holder without microcontroller) and the buzzer works.

Now I completed the circuit but it still don't work. Do I have to send it back?

These are the circuit that are working:
1) 5V regulator is working
2) IR comparator is working
3) Switches are working
4) Buzzer working
5) Motor Driver working

I don't know how to test these and suspect is spoil:
1)20 Mhz crystal (don't know how to test and suspect it is spoil)
2)Microcontroller (can write and read hex but not functioning)
3) LCD (got a row of box but don't know how to test)

[ober]

From your explanation, most probably is the crystal that cause problem. To verify whether crystal is working or not, you will need an oscilloscope. It should output 20MHz of sin wave at pin 13 or 14 of PIC Microcontroller.

If you have verify that it is crystal that cause the failure, replace it would mostly solve the problem. However, it might be quite challenging for a beginner to replace crystal. You can always send back to our office to do that, do fill in the form under support tab in our website if you need to send back.

[altan]

I just check pin 13 and pin 14 with an oscilloscope and both pin did not show any oscillation (without microcontroller) and with microcontroller it just show continuous 5V output for pin 14 and about 3V continuous for pin 13.

I will just send the circuit board back to your office to replace the crystal and check for other faults.

However, it might be quite challenging for a beginner to replace crystal.

Can explain why replacing crystal is challenging?

Thanks ober for the help.

[ober]

Can explain why replacing crystal is challenging?

oh.... this is because is not just unplug and plug again like PIC on a IC socket. Our concern is changing a soldered component is the pad being lifted off when desoldering, long period of heat from soldering gun will damage the pad.