Anyone good at circuit board design?

[cwbullet]

I tried to make it myself with eagle and I am just not good with this software. I want a small circuit like:



but without a switch. I want contact pads the touch wires to test the continuity of e-matches.

 

[cerving]

I'd be happy to help you with that, but honestly you're better off checking them with a DVM. With simple continuity check, it won't catch one that might be dead-shorted. I check every ematch with a DVM before it goes into the rocket... most of them are about 1 ohm.

 

[rocket_troy]

I use Diptrace because of the small sample of online comments I read, it appeared to be easier to use. Whether that's true or not ... dunno, but i can use it reasonably proficiently now.

TPP

 

[cwbullet]

I'd be happy to help you with that, but honestly you're better off checking them with a DVM. With simple continuity check, it won't catch one that might be dead-shorted. I check every ematch with a DVM before it goes into the rocket... most of them are about 1 ohm.

What is a DVM - Digital Volt meter?

 

[UhClem]

http://davesrocketworks.com/electronics/meter/meter.html
I fiddled around with an INA125 based design but never built one because I didn't need it.

 

[cwbullet]

I guess I could just find a way to use fixed contacts with a multimeter. I need to be able to check them quickly.

 

[cerving]

What is a DVM - Digital Volt meter?

Yes. You can get them for < $10 at Harbor Freight... not the best quality, but certainly good enough for checking ematches. I keep one in my field box.

 

[cwbullet]

I have been using a DVM. It just takes too much time when making ignitors or e-matches yourself. I will come up with a way to connect them with small contacts.

 

[cerving]

Get some alligator clips for the leads, it literally just takes one or two seconds to hook them up, and a few seconds to register on your DVM. That's one difference between the cheap DVM's and the good ones... the goods ones register faster.

 

[OverTheTop]

What about a couple of metal plates connected to your DMM, fixed in place on your bench (or clamped). You just hold each wire of your ematch onto them and read the resistance.

 

[Voyager1]

I guess I could just find a way to use fixed contacts with a multimeter. I need to be able to check them quickly.

Use a pair of these with your meter.

 

[cwbullet]

Use a pair of these with your meter.

I have tried those, It only with with low volume testing. I make them 50-100 a pop. I am trying to automate the process.

 

[cwbullet]

What about a couple of metal plates connected to your DMM, fixed in place on your bench (or clamped). You just hold each wire of your ematch onto them and read the resistance.

That is what I am think about doing.

 

[nevadagold]

If you are looking to make your own boards. Express PCB has their own design software that is easy to use and you can order boards right from the software. I have used them for quite a few projects.

expresspcb.com

 

[OverTheTop]

If your board is old-school simple then you could etch your own and not even use CAD. Get some single-sided PCB laminate. Clean copper side with steel wool so it is shiny. Draw where you want the copper to remain with a suitable marker. I have used normal permanent markers (eg Staedtler Lumocolor) in the past successfully, but there are markers designed for the purpose. I have a Dalo PCB pen from decades ago still in my drawer still. Once the design is drawn you etch the exposed copper away, typically using ferric chloride. Don't spill this on anything as it stains badly. You can warm this to speed the process or just agitate and be patient. Once etched give the board a wash, clean the pen ink from the top and drill any holes you need (or not, if you are just soldering to the surface).

I have made many simple PCBs this way in days gone by.

Whatever you do I suggest keeping the solution simple.

 

[cerving]

I remember making small proto boards with a peel-and-stick copper tape that went over perfboard... I think it was called Circuit Quick or something like that. They had various widths of tape, plus copper patterns for transistors and DIP IC's, you soldered everywhere that you wanted the tape to join. It wasn't much easier than just connecting everything with wire-wrap wire and soldering it, which is why I stopped using it. Apparently I wasn't alone... I haven't seen it around for many years.

 

[Tech 68]

We used to use prototyping circuit boards we called "blob-board"... just bridge the pads with solder.

 

[Rocketjunkie]

I use a digital Volt-Ohm-meter for checking mine. The rea cheap ones don't resolve less than 1 ohm. I use a decent one that has 0.1 ohm resolution. Expect in the somewhere around $100. I just measure the resistance of each one. They come out 1+-.2 ohms. If outside this range, I do not use them. 2 amp all fire. I only get 1 firing out of the new 9V Duracell batteries. The old Duracells would give at least 30 firings

 

[OverTheTop]

We used to use prototyping circuit boards we called "blob-board"... just bridge the pads with solder.

We use these "dot boards" as well. Very convenient. Note: DO NOT JUST BRIDGE THE DOTS WITH SOLDER. Solder is crystalline and brittle and will crack, leading to intermittent connections. Always embed a wire in the join. It only needs to be a thin one. I have seen this many times over the years.

 

[tsmith1315]

I guess I could just find a way to use fixed contacts with a multimeter. I need to be able to check them quickly.

Use a pair of metal 5-way binding posts, stick the meter probes into the holes and tighten the nut down to hold them securely.
Then you can just hold the igniter wires to the side of the posts for a reading.

 

[heada]

I use a digital Volt-Ohm-meter for checking mine. The rea cheap ones don't resolve less than 1 ohm. I use a decent one that has 0.1 ohm resolution. Expect in the somewhere around $100. I just measure the resistance of each one. They come out 1+-.2 ohms. If outside this range, I do not use them. 2 amp all fire. I only get 1 firing out of the new 9V Duracell batteries. The old Duracells would give at least 30 firings

Out of spec ematches are still good for ground uses, just not flight events. I'll use them in motors on the ground where I can dump 12v 10A+ in each one all day. At that power, it doesn't matter if you have one that is an ohm off of the ideal and if it doesn't fire, its just a walk to the line to replace it.

Perf board or proto-board should work for this. Just embed a small (~32AWG) wire in the solder and you make your own traces. I place the bare wire, use a flux pen and trace over the wire and proto-board and lay down solder. With the flux, it doesn't take long.

 

[tokind]

We use Easy EDA for circuit board layout, and have them printed by JLCPCB in one easy step. Easy EDA is chock full of useful features and includes a parts library to make component layout quick and easy. The best part is that the entire process works in a web browser. I do designs on a Chromebook.

If you don´t much mind waiting weeks for delivery — JLCPCB provides cheap and high quality production.

 

[KilroySmith]

OK, perhaps a mechanical solution to your problem is appropriate.

I second the recommendations above to use a DVM and measure resistance rather than an LED. I think you'll find it much more reliable. You can get a really cheap device (https://www.amazon.com/dp/B07FN91625), perhaps with a set of tweezer probes (though I don't know if they'd work so well for wires): https://www.amazon.com/SMD-Tweezer-Clip-Test-Meter/dp/B07L94777B

Perhaps a better way would be to modify a chip clip to make this a bit easier, rather than the tweezers. Slot the jaws lengthwise, glue a thin piece of plastic in one jaw as a seperator. It should slide into the slot on the other jaw when the clip is closed. Put two strips of copper foil on one of the jaws, one on each side of the seperator covering half the jaw. Solder wires onto the copper foil, with banana jacks on the ends of the wire to go into the meter. Now, you should be able to hold the clip in one hand, open it, use your other hand to place the leads from a starter in the clip (one on each side of the seperator), and close the clip. Read the resistance, open the clip, throw the starter in the "Good", "Weak", or "Bad" pile, pick up the next one.

 

[curtisheisey]

I use KiCad for PCB schematic entry, layout and creation of gerbers. Pretty easy to learn and use. It took me a weekend to get my first board of about 50 components complexity. Everyting worked the first time, but two footprints were a tiny bit off. The hardest part was matching the component footprints with ones that I could order. I have useed seeed studios and JLCPCB for PCB production. Both in China and about a two week turn around time. The latter has a number of compent libraries , and they have an assembly service.

 

[AllDigital]

Chuck, you really are better off using an ohm meter to check e-matches. Basic continuity won't tell you if they have a short or too much resistance. My rule of thumb is below .5 ohms I toss them out. For high quality matches, like MJG, Jeff says that the e-matches are good between .8 and 1.2 ohs. Anything below is suspect of a short and anything above is questionable to fire. The "orange ones" are less consistent and have unreliable readings after firing. Many of the orangies will short out when they cool down 3-4 seconds after firing, indicating false "continuity" but no charge left.

If you really want to design a circuit to rapidly test matches then it should give you a green light between a certain resistance range and red light if under/over. I tried to incorporate this logic into my last launch box, so I could actually see the igniter "continuity" state remotely, but the 20 foot wires, alligator clips, and other circuitry add too much resistance variation to be reliable on the pad.