whats a good way to prototype?

[strokedmaro]

Ive read in so many places about how high capacitance in breadboards are the proverbial knife in the back for pic oscillators...sure enough I cant get programs working because of my breadboard but I also dont want to etch out a board only to find that I should have made changes...anyone have any ideas on a better breadboard??

 

[3v0]

Modern PICs have internal clocks that work up to 38MHz. Even the ones that have 8MHz internal clocks work fine for most applications execpt generating video signals or building clocks.

What are you building ?
3v0

 

[Nigel Goodwin]

Ive read in so many places about how high capacitance in breadboards are the proverbial knife in the back for pic oscillators...sure enough I cant get programs working because of my breadboard but I also dont want to etch out a board only to find that I should have made changes...anyone have any ideas on a better breadboard??

Plenty of people build PIC projects on breadboards, but I don't - check my tutorials for examples on veroboard.

 

[mvs sarma]

Ive read in so many places about how high capacitance in breadboards are the proverbial knife in the back for pic oscillators...sure enough I cant get programs working because of my breadboard but I also dont want to etch out a board only to find that I should have made changes...anyone have any ideas on a better breadboard??

I know of designed artworks that failed to oscillate the PIC Micros. Layout too demands tighter restrictions, perhaps.
The best appears wiring on 'DOT Boards" compared to vero strip boards. Most circuits work well upto almost 50to60MHz should work, i believe.

 

[futz]

Ive read in so many places about how high capacitance in breadboards are the proverbial knife in the back for pic oscillators...sure enough I cant get programs working because of my breadboard but I also dont want to etch out a board only to find that I should have made changes...anyone have any ideas on a better breadboard??

I keep hearing that breadboard-capacitance nonsense. I'm convinced that it's just that - nonsense. I've never run into any problems whatsoever on a solderless breadboard, with any PIC or any circuit - big or little, at any osc speed.

I use mostly **broken link removed** breadboards and a few **broken link removed** ones too. They all work just fine.

 

[mvs sarma]

I keep hearing that breadboard-capacitance nonsense. I'm convinced that it's just that - nonsense. I've never run into any problems whatsoever, with any PIC or any circuit - big or little, at any osc speed.

I remember that you had even posted some photos of breadboad assemblies of your designs in the past. Perhaps it depends on the quality of make, and the art of wiring it, as some photos shown in this site.

 

[philba]

ditto what Futz said. Yes, there is capacitance but I've measured something like 6 pF between two adjacent rails on an SBB I have. I wouldn't try to run something at 1 GHz but a PIC crystal running at 20 MHz is no problem. I've not had any problems. It's not going to be a high precision design but it's enough for learning and proof of concept. Plus it's really quick to get something going.

 

[futz]

I remember that you had even posted some photos of breadboad assemblies of your designs in the past. Perhaps it depends on the quality of make, and the art of wiring it, as some photos shown in this site.

I have run into a few that refused to work right without proper decoupling caps on the PIC, or on other chips. But I normally don't bother with them unless something won't work.

 

[mvs sarma]

ditto what Futz said. Yes, there is capacitance but I've measured something like 6 pF between two adjacent rails on an SBB I have. I wouldn't try to run something at 1 GHz but a PIC crystal running at 20 MHz is no problem. I've not had any problems. It's not going to be a high precision design but it's enough for learning and proof of concept. Plus it's really quick to get something going.

SBB or S/L BB?
Now a days we get PCBs with the same pattern of a solder less breadboard. These PCBs, though, single sided FR4 type, work for one or two trials per board.

 

[strokedmaro]

I cant explain it any other way. I can get a program running (16f88) just fine using the 31.25 internal osc to display text on an LCD. anything above that it does not work or displays random crap....but when I took that exact pic to a friends house it works perfectly fine on his setup....just a different type of breadboard. Can't be the connections as it will work perfectly when set to 31.25KHz and nothing else is different between our setup except breadboard types

*using only internal osc.

 

[philba]

SBB or S/L BB?
Now a days we get PCBs with the same pattern of a solder less breadboard. These PCBs, though, single sided FR4 type, work for one or two trials per board.

Solderless Bread Board - I use SBB but I can see the ambiguity.

 

[skyhawk]

I cant explain it any other way. I can get a program running (16f88) just fine using the 31.25 internal osc to display text on an LCD. anything above that it does not work or displays random crap....but when I took that exact pic to a friends house it works perfectly fine on his setup....just a different type of breadboard. Can't be the connections as it will work perfectly when set to 31.25KHz and nothing else is different between our setup except breadboard types

I assume that when you switch from 31.25KHz to higher frequencies the adjust your delays in your LCD display routines accordingly.

I've never had trouble running at 20 MHz on a breadboard. Right now I have a simple 16F54 running on a breadboard with a 20MHz resonator driving an "LCD billboard" with no problem. I have the same good results with circuits on vector board even when I lay the circuit out badly, and the crystal is about an inch from the PIC.

 

[3v0]

I cant explain it any other way.

This is a dangerous state of mind. You need to be suspicious of everything. Paranoia pays.

3v0

 

[futz]

I've never had trouble running at 20 MHz on a breadboard.

I've done many 20MHz PICs with external crystal osc on breadboard (all worked fine), and 120MHz internal osc on 33F4013 (also worked perfect), and lots of other speeds in between.

Hey strokedmaro, can you show us a photo or three of your (not-working) setup, and maybe a schematic if it's not obvious in the photos? Set your camera to macro mode, flash disabled, use the 2 second timer, provide LOTS of light and hold as still as you can (brace against something). Some source code would be a good idea too.

-------------

Other questions:

1. How are you powering your circuit?

2. Do you have decoupling caps at the VDD/VSS pins of the PIC?

3. Do you have a 10K to 33K pullup resistor on the MCLR pin?

If it turns out that your breadboard is faulty, chuck it out and replace it. They aren't expensive enough to be worth wasting a lot of time tinkering with.

 

[Pommie]

I have never had a problem with capacitance. This is probably because I normally don't go over 20MHz but I have done USB stuff running at 48MHz without any problems. Besides, how much capacitance can there be between 2 strips with a few square mm of area and separated with over a mm of plastic. I really think the capacitance problem is very overstated. I was curious and so I worked it out, 40mm² (10x4) area and 1mm of some plastic (say polycarbonate - Relative permeability 2.8). I get 1pF. Completely irrelevant unless your building RF circuits. For the curious I did (8.85*10^-12 * 2.8 * 40*10^-6)/1*10-3.

Mike.

 

[philba]

I just measured one with my DMM. I stuck 2 short pieces of wire into adjacent rails on my cheapest SBB. With DMM leads unconnected (but close), I get 37 pF and connected I get 42 pF. Not exactly Myth Busters but if there was a lot of capacitance, it would have registered higher. I think 5 pF can't be very far off.

 

[3v0]

I am curious if there is any difference between the various BBS. There are a lot of people ones that look the same as the one I posted a short while mack.

 

[atferrari]

What kind of difference

I am curious if there is any difference between the various BBS. There are a lot of people ones that look the same as the one I posted a short while mack.

Are you talking of durability or of a smooth insertion?

The best I got were some I bought from ACE (USA) some 25 years ago, still in use.

The worst, a French one (well, bought in France) that was a disaster mechanicalwise.

There is another (also American origin) which seems to require very small diameters of wire to be inserted. When extracting them you feel that wires are stuck somehow. And they costed dearly!

ALL my projects including micros up to 8MHz clock, worked OK in breadboard.

I resorted to perfboards when I knew I had lot of connectors involved and massive wiring was required. Lack of mechanical stability has been the most frequent reason for hard to catch failures in my designs.

 

[3v0]

I was thinking about durability.

A dim memory tells me that using wires larger then 22awg is bad for the SBB. Yet it is common to see people, including me, using pin headers.

For me, making a PCB is easy enough that I do not often breadboard an entire circuit. Just the bits that I have real questions about.

My students are starting from the ground up and need the SSB.

I discontinuted using my 25 year old radio shack SBB's. I nearly tossed them out but realized they work as an alignment tool when building a PCB with multiple pin header connectors.

3v0

Are you talking of durability or of a smooth insertion?

The best I got were some I bought from ACE (USA) some 25 years ago, still in use.

The worst, a French one (well, bought in France) that was a disaster mechanicalwise.

There is another (also American origin) which seems to require very small diameters of wire to be inserted. When extracting them you feel that wires are stuck somehow. And they costed dearly!

ALL my projects including micros up to 8MHz clock, worked OK in breadboard.

I resorted to perfboards when I knew I had lot of connectors involved and massive wiring was required. Lack of mechanical stability has been the most frequent reason for hard to catch failures in my designs.