Solderless breadboard with PIC's

prototype solderless breadboard power supply

I have been using a solderless breadboard to prototype my PIC projects. I have been getting unreliable operation and unpredictable behavior. I am guessing that it is because of power supply noise and/or oscillator interference. I used several .1µF caps along the supply rail as well as a 10µF tantalum cap near the power input of the breadboard. I also placed the crystal as close to the PIC as possible, but I still have problems. I do not have the money to buy dev boards nor the time to design a PCB for every project idea. I was considering using an LDO, or a 7805. Perhaps an ATX power supply with current limiting (they supply an enormous amount of current), and additional filtering. As for the crystal, I don't know. Does anybody have any suggestions to clean up the power supply and oscillator? Any help would be greatly appreciated.

pic breadboard circuits

Computerman29 said:

I have been getting unreliable operation and unpredictable behavior.

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Please give us more details. What did PIC do taht you didn't expect? Do you have motors, home-made HAM transmitters of other sources of EMI connected to your board?

Computerman29 said:

I used several .1µF caps along the supply rail as well as a 10µF tantalum cap near the power input of the breadboard. I also placed the crystal as close to the PIC as possible, but I still have problems.

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You're doing the right things. My first breadboard followed the same rules and it worked reliably for years. Try to increase the crystal capacitors by, say, 5pF. Have you tried to use clock oscillator instead of a crystal? Try to put a 10 Ohm resistor or an inductor in series with the oscillator power supply pin. Connect a decoupling cap (ideally both 0.1uF and 10uF electrlytic) directly to the pin.

Computerman29 said:

I do not have the money to buy dev boards

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Dev boards are a waist of time anyways (IMHO). It's better to be debuggin your own design instead of someone elses.

solderless breadboard current capacity

I used 16F84A, 16F917, 16F877A and 16F628A. I have an Associate in Electronics Tecnology. I am just starting microcontrollers. I am using DIP-4 clock oscillators running at 4MHZ, and 20MHZ. I have also used crystals with 33pF caps. My circuits are mainly pushbutton switches on the inputs and LED's on the outputs. I even used a chip from ON Semi to debounce the switches. I eventually hope to implement I2C to control brightness and flash rate of LED's, with LCD or LED display and a keypad. I have soldered two projects on perfboard (plain board with a million holes drilled in it) and they both worked fine.

The problems I am experiencing are: works for a while and then quits, doesn't work at all, or various unpredictable things. I am certain that the problem is hardware and not in my code.

solderless breadboard

Some bad quality breadboards have strays capacitances in theirs contacts. When using PIC with external crystal + load capacitors the breadboard capacitances may influence the oscillator functioning and can stop it. Try to use PIC with internal oscillator to make tests and then come back to crystal when the circuit is debugged.

pc power supply for breadboard

Kender: What value of inductor do you suggest?

rkodaira: The breadboard is a 3M brand. It is the board I used while in college. It is in good condition - hardly used since then. It is, however about 7 years old. Could that have something to do with it?

What are you using for a power supply now??? I use a pc power supply on the 12v side and in the PIC circuit I run a 7805 with a 10uF on the highV side and a .1uF on the 5V Side with no problems... You might want to try using a "reset" chip from microchip... It is a votage detector that you put on the mclr pin so when power is applied to the circuit, the voltage wont ramp up and sometimes lock up the pic...... good luck

I use solderless breadboards with pics, no problem.
Put a .1uF across the pic, nearest holes to the pic power pins. You don't need a fancy power supply. Any moderate qualtity supply should be fine.
I use 7805 with only a .1uf cap and no 10uF.

Computerman29 said:

Kender: What value of inductor do you suggest?

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I would say, from 10uH upward. The bigger inductance the better. Although, make sure that the inductor can handle the current. Typically, if you have a family of inductors with the same mechanical dimensions, the current rating is inversely proportional to the inductance in such family.

It's conceivable that that your power supply goes into the oscillatio or just shuts off. If you're not doint it already, have a voltmeter (or a scope) constantly hooked up to the power supply. You might be ableto spot something interesting. Come to think of it, you could measure (or asses) the noise parameters on your power supply and post them here. That would give us a clue about how to fix it (and it would look good in the report too).

BTW, what school are you getting your degree at?

I graduated from Ivy Tech State College, Valparaiso, IN in 2001 with an AAS in Electronics Technology. I'm a bit rusty. I'm teaching myself PIC's to start a business.

I am using 3.6-4.8v NiCd AA battery packs for my power supply (with filter caps.) I also use a 4.7K pull-up resistor on MCLR.

youre only using 4.8v ni-cad's? I would use the "reset" chips from microchip... I used to work for a company that made wireless controls with pic's and we would always use a reset chip on every new design... Aso I would try loosing the resistor on the mclr pin frist.... Try this link and do some research on the voltage detector www.microchip.com/stellent/idcplg?I...+Sheets&section=Data+Sheets&ssUserText=MCP111

I am now using a 9v wallwart, a Fairchild KA7805A with 1000µF and .1µF caps on both the low and highside. Measures a steady 5v. I have not built any new projects yet though. I am waiting for my ZIF sockets that I ordered for my programmer. I don't think I will have any further problems. I'll let you know when I receive my ZIF's. Thanks to everyone for helping.