Antenna tower obstacle light flasher circuit?

crutschow

Joined Mar 14, 2008
34,280
A breadboarding alternate to a Vector board, which requires soldering, is a plug-in breadboard, if you plan on building a PCB afterwards.

Otherwise a soldered Vector board can be used as a permanent board, in place of a PCB.
 

Thread Starter

Rabbit H

Joined Aug 5, 2016
153
By any chance do you have a link for project boards set up for edge connectors?

Harvey
 
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Which circuit did you choose to go with? The one suggested in post #34? Attached is a quick work-up for you that you could send to OSH Park for fabrication. They do multiples of 3 of your board (minimum order is 3), but they're really cheap; this board is coming in at $14.15 (for the order of 3)... order 3x the parts, and you have two backup boards!

Ironically, AAC doesn't allow .brd attachments -- just remove the .txt extension.

It's probably not the greatest, but it should do the trick (and I'm posting it here in hopes that @crutschow and others can vet it), and might save you some work :)

Here's a parts list for it from Mouser: http://www.mouser.com/ProjectManager/ProjectDetail.aspx?AccessID=238521fb7d
Right now the design uses trimmer pots which give you great precision at 20 turns, but they're kinda pricey. If you find some acceptable board-mount pots that are considerably cheaper, it should be trivial to tweak the design. The current pricing is ~$24 for components to populate three boards.

J_IN is for your supply connection (15VDC according to crutschow's schematic), and J_OUT is your signal (and ground) output connection.

Below is the schematic, to confirm that I didn't omit or mis-wire anything, as well as the top and bottom mockups of the board as OSH Park sees them.

P.S.: Please IM me directly if you need it modified or have any questions... otherwise I may miss your reply :eek:



 

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crutschow

Joined Mar 14, 2008
34,280
DJ, that's a neat layout. Unfortunately the modified schematic I posted in post #37 is preferred, which uses a TL431a with an added pot for adjustment of the clip level, in place of the fixed zener.
Interestingly, the TL431a is actually about the same price as the zener.
If Harvey wants to go with your board, could you modify it to include that?
Thanks,
Zapper

Edit: I don't see power and ground on the schematic for the op amp, and I don't see any ground connections to the ground plane on the board (I expected to see thermal relief pads to the ground plane. Did I just miss seeing them?).
 
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Thread Starter

Rabbit H

Joined Aug 5, 2016
153
Good Morning Guys. It looks like I shut down my computer too early last night because Doktor's post has really ramped up my plans. (Okay, I excite easily nowadays! :D )

Doktor,
Yes, I'm leaning towards Crutschow's modified circuit (post #37) with your board layout if for no reason other than the enthusiasm that the two of you have shown towards my project. I especially appreciate the parts list that you put together at Mouser and your initial price check with OSH Park for board fabrication. Yes, I have no problem buying and building three boards. (I can't get over how cheap it is to fabricate three boards!!!) One thing I learned in the military is to always have a backup ready.

Any chance you can tweak the board to accommodate Crutschow's suggestions above (post #47)?

The "pricy" trim pots are acceptable.

Is there enough space around U1 to accommodate a socket for it?

Again, thanks Guys!

Harvey
 
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Thread Starter

Rabbit H

Joined Aug 5, 2016
153
The weather got a bit dicey yesterday morning. The location is a private airport on the west side of Houston and the view is to the west. This cell just barely missed us as it moved northward. This weather system is the same one that caused so much flooding in southern Louisiana last week. While we've received a lot of rain ourselves over the past week, thankfully it hasn't been as devastating on us as it was on Louisiana!

17 Aug 2016.PNG

The tower's twin red ob lights (that we're designing the modulator circuit for) can be seen just above the platform railing on the right side of the beacon. This tower is a restored (and relocated) 84 year old survivor of the 1932 Transcontinental Airway Beacon System, which provided visual (i.e. lighted) navigational assistance for the early coast-to-coast airmail pilots. (Often through weather much like today's!)

Harvey
 
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DJ, that's a neat layout. Unfortunately the modified schematic I posted in post #37 is preferred, which uses a TL431a with an added pot for adjustment of the clip level, in place of the fixed zener.
Interestingly, the TL431a is actually about the same price as the zener.
If Harvey wants to go with your board, could you modify it to include that?
I should be able to work that up if I have time tonight :)

Edit: I don't see power and ground on the schematic for the op amp, and I don't see any ground connections to the ground plane on the board (I expected to see thermal relief pads to the ground plane. Did I just miss seeing them?).
Ground is tied via thermals (ground plane is on the top because there are a couple of places where the traces run within the isolation tolerances of the polgygon that the ground plane would start to look more like a jigsaw puzzle)... the thermals are hard to see because of the solder mask layer.

Remember on the board bottom image the pinout is flipped, so pin 4 (+V) is in the right column of the DIP pins. It's got a trace running directly to J_IN (which also squeaks between pins 2 & 3 to go to the resistor for the Vref used in the amps). Eagle CAD has basically a "hidden" connection to the +V and -V nets from most IC parts, so there's nothing in the schematic that shows the power connection, it's just implied.
 

crutschow

Joined Mar 14, 2008
34,280
Even if you use the PCB, I would recommend breadboarding the circuit first, since all I've done is a simulation of the circuit, which is not an absolute guarantee that it will work in practice.
You could do that fairly simply without any soldering, using the plug-in type breadboard I referenced in post #42.

Doktor, there's one thing I forgot to include on the schematic and that's a decoupling cap.
Please add a 0.1μF ceramic cap directly between pins 4 and 11 on U1 when you redo the board.
Thanks,
Zapper
 
@crutschow:

Will putting the decoupling capacitor next to pin 4 on the IC socket (parallel to it, with the other lead in the ground plane) be sufficient?

Do you think a larger electrolytic (maybe 10uF-47uF) next to the input (J_IN) would be a good addition too? The circuit strikes me as potentially susceptible to noisy power since the reference voltage is based off a voltage divider.

Your thoughts?
 
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crutschow

Joined Mar 14, 2008
34,280
Will putting the decoupling capacitor next to pin 4 on the IC socket (parallel to it, with the other lead in the ground plane) be sufficient?

Do you think a larger electrolytic (maybe 10uF-47uF) next to the input (J_IN) would be a good addition too? The circuit strikes me as potentially susceptible to noisy power since the reference voltage is based off a voltage divider.

Your thoughts?
Yes to the first.
Adding the electrolytic next to the power input is also a good idea.
Now that you mention the reference voltage, let's go whole hog and also add a 0.1μF cap from the junction of R6-U6 to ground. :D
 

Thread Starter

Rabbit H

Joined Aug 5, 2016
153
Even if you use the PCB, I would recommend breadboarding the circuit first, since all I've done is a simulation of the circuit, which is not an absolute guarantee that it will work in practice.
Yes, you're absolutely right. I got caught up in the excitement of possibly having the finished product in my hands soon and completely forgot that the circuit is still unproven. I got an e-mail this afternoon saying that my Velleman light dimmer kit has been shipped. Once I get it built, we can focus on your modulation circuit. (The kit was shipped by USPS so we might be looking at around Easter of next year.:rolleyes:)

Harvey
 
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Thread Starter

Rabbit H

Joined Aug 5, 2016
153
Guys,

What do you suggest for the modulator's 15vdc power supply? Wallwart, or something a little more regulated and filtered such as the Velleman K1823?

Harvey
 
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crutschow

Joined Mar 14, 2008
34,280
The circuit will also work at 12V so any regulated 12V-15Vdc wallwart should work fine.
The circuit only requires a few mA so a minimum size wallwart supply is all that's needed.

The Velleman power supply kit requires a raw DC input voltage so you would still need a transformer and rectifier to supply that.
 
Updated board... finished it up on the train today. I used an inline layout for the TL431a so you can pop in a 3x1 socket rather than soldering the regulator directly. I also added silkscreen labels on the trim pots for clarity, as well as a values list on the back of the board for reference if something ever lets out its smoke.

I will hopefully be able to update the cart @ Mouser tonight to include the new components.

Top of board:


Bottom of board:


To help visualize the grounding and connections, here are the top/bottom copper layers:



BOARD (.brd file): https://drive.google.com/open?id=0BzoF3M9qOL2ZNkQ2SGdFd3dWdmc
 

Thread Starter

Rabbit H

Joined Aug 5, 2016
153
Wow, that looks REALLY professional! You even included our monikers in the silkscreening - A nice touch!

It looks like computers have ended the days of sitting down at a drafting table for hours with a posterboard and bottle of india ink while a 35mm camera on a tripod waits nearby! (You see, Crutschow... I HAVE etched board layouts before! :) )

Many, many thanks!

Harvey


For Sale...
35mm camera and tripod (Note: Has some india ink fingerprints.)
Drafting table with LOTS of dried india ink puddles.
:D
 
On the board file itself I corrected an errant trace that was out of position from moving components around on the board (you can see it most clearly in the bottom copper layer, toward the upper left). It's not going to break anything, but I'm a bit OCD about the layout, heh.

Also, if/when you get this made, be aware that the hole next to R9 is a just a cheater via, and shouldn't have anything in it. R9 had to connect to U1 pin 8 and C2, and I didn't want to have any traces wrapping around the outsides of J_IN or J_OUT, so I ran a short top trace to jump over. I also didn't want to nearly cut the ground plane in half, so I used the via to drop back to the bottom layer as soon as I got over the obstructing trace.
 
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