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I was wondering if making a low frequency RF circuit on a breadboard is viable.

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    \$\begingroup\$ In a laboratory exercise i once built an 100MHz sine wave oscillator on a breadboard. We even added a mini jack to it and modulated it with music playing it on a handheld radio. It worked like a charm. I don't see any problem in 125kHz, just make sure to take care of the wiring. \$\endgroup\$ – Linkyyy Mar 20 at 17:19
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    \$\begingroup\$ By breadboard, do you mean a solderless breadboard? Or soldered protoboard? \$\endgroup\$ – Toor Mar 20 at 18:13
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    \$\begingroup\$ Should be ok. Here at my university, we have the second year students build a 5 stage 100KHz broadband opamp amplifier with 100dB gain on a breadboard! A bit mean for a lab, but many have it working. You do need to be careful with your layout though. \$\endgroup\$ – Adil Malik Mar 21 at 1:25
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    \$\begingroup\$ @Linkyyy Since you want to give OP an answer you should do it in the answer section. \$\endgroup\$ – pipe Mar 21 at 8:42
  • \$\begingroup\$ @AdilMalik Same comment to you as to Linkyyy and everyone else who wants to avoid the policy: You're trying to answer the question in a comment. Why? You have enough reputation to understand why this is bad, and you must have seen the explicit message to avoid it hundreds of times by now. You bypass the quality vetting that the whole Stack Exchange was designed to do and you push your 2 cents opinion before everyone who took the time to write a real and helpful answer. \$\endgroup\$ – pipe Mar 21 at 8:47
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In my experience, yes, but you may need to take a few things into account.

  • Some breadboards are better than others. The maximum frequency I've seen operating cleanly and reliably on a breadboard is 2 MHz. I've also seen breadboards that couldn't handle 200 kHz.
  • You need to consider the maximum frequency present on the breadboard, not the largest "fundamental" frequency. For instance, a square wave signal (such as a clock or the 555's output) have very large harmonics up to maybe 5 or 7 times their fundamental frequency. If the breadboard can't handle these, then the clock will become distorted (low-pass filtered); additionally, if those harmonics spread through the breadboard, they'll distort potentially all your signals.
  • Bypass capacitors become important as the frequency increases. Put one cap everwhere a circuit connects to the supply or ground, and you may have to sprinkle them around wherever high-frequency harmonics appear.
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    \$\begingroup\$ I bought a bunch of electrolytic and ceramic caps with a 0.1" lead distance to sprinkle on breadboards, especially useful to place between the rails. \$\endgroup\$ – pipe Mar 20 at 17:06
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    \$\begingroup\$ I've seen 2kHz circuits fail on breadboards. Of course, that was done by someone who was in the process of getting a clue that big loopy wires may not be the best thing in an analog circuit. \$\endgroup\$ – TimWescott Mar 20 at 17:23
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    \$\begingroup\$ @TimWescott That's an excellent point that I forgot to include. You need very neat wiring with short cables and leads if you want a high-frequency breadboard circuit to work. \$\endgroup\$ – MBaz Mar 20 at 18:01
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    \$\begingroup\$ @TimWescott I've been that someone when I first built a circuit at school. :) \$\endgroup\$ – Graham Mar 20 at 20:44
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    \$\begingroup\$ I once accidentally made a 50MHz oscillator with two transistors and some resistors only on a bread board. It kind of gives you an idea of how much stray reactance there is. \$\endgroup\$ – Alex Cannon Mar 21 at 2:03
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If you are insanely attentive to layout, yes. That means:

  • Bypass everything with as short of wires as you can,
  • Lay your wires down flat on the board (which pretty much means you'll be doing a lot of bending and possibly custom-cutting of wires). Big loops will kill you for sure.
  • Be willing to use twisted-pair, or even small coax to go from one "major" stage to the next (i.e., if you're putting multiple breadboards together, use transmission line).
  • Position your components so that the sensitive connections are short.
  • And, of course, everything that I left out.
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  • \$\begingroup\$ Note that there are sets of pre-cut and pre-isolated wires with different breadboard-friendly lengths. \$\endgroup\$ – Jonas Schäfer Mar 20 at 19:30
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    \$\begingroup\$ @JonasSchäfer true. I've always felt it's more convenient to get a few rolls of 24-gauge solid wire and cut and strip as needed, rather than digging around in a box. But -- to each their own. \$\endgroup\$ – TimWescott Mar 20 at 19:40
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    \$\begingroup\$ Not meaning to criticize – I found this info useful for the OP. There are also sets with colour-coded and separated wire-lengths so that it’s not so much digging as grabbing exactly what you need. If you’re comfortable with cutting and stripping wire (I always get the length wrong), that’s probably overkill though :) \$\endgroup\$ – Jonas Schäfer Mar 20 at 19:50
  • \$\begingroup\$ @JonasSchäfer I wasn't meaning to criticize, either -- just pointing out that there's an alternative. I tend do do things slightly different than other people's preferences, so I'm not about to be the first one to step up and say that it's wrong to be different. \$\endgroup\$ – TimWescott Mar 20 at 20:02
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    \$\begingroup\$ You know that this is 125KHz, not 125MHz right? Of course if it's a 125KHz square wave it's really much higher than it would be as a sine wave so the edges could be rounded a little bit. \$\endgroup\$ – Alex Cannon Mar 21 at 3:24
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Yes, it's POSSIBLE but is never going to be as stable as a PCB. Best you can do is avoid wires crossing, keep them as short as possible, and ensure your connections are good.

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Actually, in the early days of radio when RF was below 500,000 CPS *** , most gear was built on a wooden breadboard with no concern for stray coupling. And it worked (sometimes). Good luck with your Branley coherer and watch out for the wouff hong.

*** CPS is a unit of frequency named for Charles Proteus Steinmetz.

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    \$\begingroup\$ A wooden breadboard is completely different in every respect that matters - this is an anecdote not an answer \$\endgroup\$ – Chris Stratton Mar 23 at 16:16

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