Does the PCB ever work on the first try?
Always breadboard your circuits first before porting them over to a printed circuit board to save debugging time and money.
Last updated February 2019
“Did you breadboard this circuit?” is a common question I ask when I’m doing a review of a schematic and the accompanying printed circuit board (PCB). If the answer is yes, I smile. If the answer is no, I cringe inside and try to understand why the circuit wasn’t breadboarded. Was it ego or confidence, or was it a limitation? If it’s ego, you need to check yourself. They say things like “I’m a senior engineer, I don’t need to put my circuits on a breadboard. I didn’t get to this position due to my lack of intelligence.” The confident one says things like “I’ve done this before, so I know it works.” Sure, if it’s the same circuit that you’ve put on a breadboard before, save yourself some time and skip that step. A more common reason is the limitations. What kind of limitations? There are many, so I’ll only cover a few.
Have you ever tried to breadboard a surface mount chip before? It doesn’t work right out of the package. You need to purchase or design an adaptor board. For example, say I want to test a SOP-23 package. I need to purchase this board or design my own to be able to insert it into the holes on the breadboard. How about an integrated circuit (IC) that has hundreds of pins? I don’t think you want to sit there and wire all those pins. Maybe you are testing an IC with high speed signals. You would need to length match each signal so that they have the same wire delay. It’s much easier to tune the lengths of the signal traces in PCB software than it is to get each jumper wire cut exactly to length.
What about the amount of current? Maybe you’re trying to power a load that requires 20A. You definitely don’t want to run that through a node on the breadboard, let alone the small gauge jumper wires.
Let’s say you skipped the breadboard and went straight to the PCB. The descriptions for pins of an IC in a datasheet can be confusing. Do I pull this signal high or low? Do I need this extra resistor or capacitor? Can I leave this pin floating? You take a guess. You have a chance to be right or wrong, but if there’s a high chance of routing the pin wrong, you run the risk of having to respin a new board. This results in time and money – your time having to redo the schematic, then having someone do a review on the revisions and your money since you have to put in a new board order.
What did we learn?
- If you can put your circuits on breadboard, then do it.
- You need to make adapter boards to be able to breadboard surface mount ICs.