Does this prototype meet a commercial standard for acceptability--knowing that it is a prototype? In other words, will my Western (USA) customer be upset when he sees it, or will it go by unnoticed as another purchased product?

This PCB board always receives a TTL signal when powered on, so no need for resistors (I believe).

A five volt DC power supply sends power to the capacitor and the capacitor to the ICs. The power cable comes in the DB15. The TTL signals (2 of them) come in the DB9. The output goes out the BNC.

The two ICs are side-by-side, is this too close?

The connector for the BNC uses two wires and the remainder were severed.

The plastic enclosure was purchased at the electronics market.

prototype board



1 Answer 1


The size of the box is limited by the connectors so it is a reasonable enclosure and layout for a splitter type box. Without more information about the circuit it would be hard to say anything else.

The spacing of TTL's is fine (if it works), if this is manufactured in quantity it is unlikely your client will spend the extra $.03 a unit for DIP sockets so the spacing between chips will actually improve. On the other hand TTL logic has been available in SMD sizes for decades and all that extra board space is a huge cost for a product like this manufactured in quantity so it entirely depends on what your client intends to do with the device with regards to the suitability of the circuit design. .

In terms of acceptability as a prototype see below for comments by category


In terms of a delivered product, it depends on what you are expected to present. For something with so few components I would spend more time making cleaner holes for the connectors to improve presentability of the enclosure. You may also want to consult your client about the type of cables being used. They may have hooded DB-15 connectors that would have trouble fitting in that opening, they may also have shielding/grounding requirements for case continuity between DB-15 sides. Additionally PCB mounted connectors that are roughly handled tend to break solder joints so physical screws may be necessary. This looks like an electrically simple device, the professionalism of your design is largely based on a clean look (good mechanical engineering) and a reliable (i.e. bombproof) assembly.


If this is a one off for a private client it is probably OK to leave on a protoboard (but check with them). If this is a something for a corporate client that needs 5+ copies or a bid for a bulk manufactured design the client will expect a PCB. I would have a PCB layout ready to replace the protoboard at the very least and ideally already fabricated. Generally speaking US companies and consumers will expect even small electrical jigs like this to be manufactured on PCB's.

Two layer pcb's in reasonable dimensions can be made quickly and shipped internationally, there are any number of PCB houses that can do this for you. Some will even provide you simple layout software with integrated cost calculators that is more than adequate for this application.


At the end of the day all of this depends on what the expectation of the client is at this stage. If this is a final prototype for a purchasing decision it is probably inadequate from a professional point of view, as an intermediate stage in development with a more relaxed professional relationship it may be fine. This is a prototype yes, but it does not demonstrate that you are ready to produce a final product tomorrow. In the US or otherwise I would expect any serious client to expect a final prototype for inspection to be close to or exactly the same as the delivered product (minus last input by client).

  • \$\begingroup\$ resistors, or some other ESD prevention network is always a good idea where external signals are involved. if you send your device to a distant land and it fails as soon as the customer connects the cable that will reflect badly on you. \$\endgroup\$ Jul 13, 2015 at 10:42
  • \$\begingroup\$ @Jasen good point. Like I said it is hard to give circuit advice without knowing more about the design and requirements. So I kept to what I could see. \$\endgroup\$
    – crasic
    Jul 13, 2015 at 10:47
  • \$\begingroup\$ My experience with protoboards is different from crasic's. For production, sure a PCB is expected. But for low-cost one off's where laying out a PC board would add significant cost or proof-of-concept prototypes that are expected to be updated, I've found that clients don't mind protoboards. I either ship them in an enclosure (those cutouts need to be MUCH neater!) or as a bare board, with the underside protected. \$\endgroup\$
    – lyndon
    Jul 13, 2015 at 12:38
  • \$\begingroup\$ @Lyndon I tried to be clear that client expectations need to be determined. When a client needed a 5 run of connector adapter we were expected to lay out and ship a pcb in 4 days. Ymmv if op expects to make more than a handful of these a pcb will probably be necessary \$\endgroup\$
    – crasic
    Jul 13, 2015 at 15:47

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