2
\$\begingroup\$

I have a project I want to wire up on a prototype board. I know the peak voltage and current expected at each contact point. But how can I tell whether the board can handle it? If it can't then it will arc (too much voltage) or overheat (too much current) and ruin my work.

I haven't been able to find voltage or current ratings on any of these things. But the spacing and cross-section of the plating varies significantly across designs, manufacturers, etc. Here's what I have on hand:

  • Strip-board: I.e., perforated board with copper traces running across the rows of holes. This is nice because I can use each row as a power bus and interconnect. Except that I don't know how much current the traces can carry. Does one commonly "proof" a strip-board by ramping current through a trace until it starts to heat, and then calculating the current capacity based on the heating rate? (Another excuse to pull out the thermocouple!) Or if I'm concerned should I just layer solder over the traces that are carrying significant current? Or avoid these altogether?

  • Protoboard: Perforated board with solder pads around each hole. Some are "through-plated" (meaning the conductive plating runs through each hole to the solder pad on the other side of the board). I don't have to worry about current here because I'm making wire interconnects. But I still have to worry about voltage: Those little solder pads are very close together, and at some voltage level the electricity will arc across them. At what voltage level does one start to get concerned about arcing on this type of board? Is there a reliable way to "proof" these boards for a particular voltage level?

  • Unplated perf-board: I.e., solid plastic with molded or drilled holes. When in doubt I fall back on this: It has no conductors and everything is wired so I can ensure all conducting paths are sized, spaced, and insulated for the working voltage and current. But, strangely, this is the most expensive board by unit area! (Why?)

\$\endgroup\$
  • 1
    \$\begingroup\$ If you have a circuit so extreme you're worried about such things, just spin a PCB and be done with it. \$\endgroup\$ – Matt Young Apr 2 '16 at 18:52
  • 1
    \$\begingroup\$ @MattYoung - It has been a while since I've looked at making, or having made, a PCB. Maybe it's cheap enough to outsource now for a quantity of one, and maybe I'm not weighing the time of doing it myself correctly. But for true "prototyping" I'm not only potentially swapping out components with different specs, but maybe adding features as I develop. \$\endgroup\$ – feetwet Apr 2 '16 at 19:06
  • \$\begingroup\$ I'd recommend building one of each board & testing them with the most extreme conditions (+20%) that you expect your designs will encounter. Empirical knowledge is invaluable. \$\endgroup\$ – zeffur Apr 2 '16 at 19:24
1
\$\begingroup\$

Since the resistance (R) of any plated through-hole or copper trace on a proto-board is very small, no matter the voltage, not much power (P=VxI=I^2xR) will be dissipated.

What you are really asking is the power rating of your proto-board. Power is related to heat which will be the cause for damage. Most proto-boards will be fine for many applications, even high voltage. If you are working with high voltage, your concern should be for your own safety rather than the proto-board.

In conclusion, proto-board should be able to handle high currents because the resistance of a copper trace or plated through-hole is very low.

P=Voltage x Current=Current^2 x Resistance -- if resistance is small in this equation, then you have low power through the copper trace / plated through-hole


Your concern should now be focused on the power rating of the rest of the components in your circuit.

In a PCB, power ratings of a trace will depend primarily on the width and height of a trace (height in the US is usually defined in oz, ounces of copper per unit area).

\$\endgroup\$
  • 1
    \$\begingroup\$ The concern with high voltage on the board would be that it could arc to another component on the board, creating a short circuit. And maybe not even destructively, but certainly with very confusing results! \$\endgroup\$ – feetwet Apr 2 '16 at 19:08
  • \$\begingroup\$ Arcing is related to the distance and voltage between components. This is highly unlikely, unless you are dealing with voltage above mains level (110, or even 220 V). \$\endgroup\$ – abstack Apr 2 '16 at 19:11
  • \$\begingroup\$ At what voltage does it become a concern? When I say "high voltage" I'm thinking of potentials up into the kV range. Of course I can control the spacing on the board. But I'm having trouble thinking: If contacts A and B will arc when on adjacent pads, does separating them by n pads ensure they won't arc? Or is there something like a plated board "breakdown voltage" where, if the potential difference of any two contacts exceeds that level then they will arc no matter where they contact the board? \$\endgroup\$ – feetwet Apr 2 '16 at 19:17
  • 1
    \$\begingroup\$ @abstack - you wrote a lot, but, you really didn't answer any of the OPs questions. \$\endgroup\$ – zeffur Apr 2 '16 at 19:20
  • 1
    \$\begingroup\$ Ha.. Ok now we are talking. You should revise your question to: (can protoboards handle kVs?). The answer to your question (if you can provide a semi-accurate number of kV) can be found using a trace-width calculator (google.com/…). You may also look for a through-hole calculator. I can't say whether these tools are accurate above a certain voltage. \$\endgroup\$ – abstack Apr 2 '16 at 19:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.