Updated: Build Files For 2-3 Aspect Signal Actuator; Common Anode LEDs; Video Added

Just adding the Excel BOM files for these boards, both domestic and offshore versions.

Total costs are about $15 for domestic and $5 for offshore. About the usual difference. One huge difference is $6.10 each for OSH Park boards, versus less than a dollar for offshore. I have also included .1" pitch screw terminals for both, though these are not available domestically from what I can see. You can reduce the price by about one dollar  a board by eliminating these and going with a lesser expensive option such as DuPont connectors. Another option is to simply solder wires to the board connections. There are lots of choices.

These BOM's are for a full build including bridge rectifier and filter capacitor (not necessary for DC power supply) and an onboard 7808 regulator, which is not necessary for a DC supply up to about 12 VDC. These components should probably all be included for use with an AC supply however.

I can add a pdf version if anyone needs that option. Rod

Rod: Can you piece together a short video? I'd love to see this in operation. Please demonstrate the adjustments to timing with the pots.

Thanks!

  -- Leo

Consolidated Leo posted:

Rod: Can you piece together a short video? I'd love to see this in operation. Please demonstrate the adjustments to timing with the pots.

Thanks!

  -- Leo

Bad timing Leo; I just took the breadboard circuit apart, and my first order of boards has not arrived just yet. Once it does I will be happy to assemble one and run a short video for a demo.

I am also attaching the Excel spreadsheet for finding the correct value of R7 ballast resistor for the Vcc voltage level and the led intensity desired.

Cheers,

Rod

Got my first order of boards for this project today, and got one built. Works quite well:

I hope that video has uploaded OK. The red release timing was set to minimum for the video but it can be adjusted up to more than 30 seconds with the trimmer pot. The yellow delay is set to 10 seconds but that can be changed also.

Seems to work very well. This is an early version and lacks provision for an LM78xx voltage reg. But the version uploaded earlier above has the reg provision.

Rod

Rod, can I get you to send me the Diptrace files for this one?

gunrunnerjohn posted:

Rod, can I get you to send me the Diptrace files for this one?

No problem John, I will email them to you shortly.

Rod

So I have encountered an unanticipated problem with this first board build.

All my testing on the BB was done using a momentary pushbutton switch to simulate block occupancy, and I think RTR12 used the same idea. Now with this first board build I was experimenting leaving the BOD contacts connected for an extended time, like a train travelling through the block. I found that when you release the BOD, the red signal goes immediately to green, surprisingly.

It looks to me like the timing sequence starts as soon as the BOD contacts are tripped, instead of initiating when they are disconnected. Thus, when the BOD is opened, the release timings have already expired, and it goes straight to green. Not as we intended at all.

So anyone who is planning on ordering boards using the gerbers posted earlier, better hold off until we get this solved. For anyone who has already ordered boards, maybe see if you can cancel or put your order on hold. My apologies for any inconvenience. Hopefully we can get this solved quickly.

If anyone has any advice as to a resolution, that would be appreciated also.

Rod

The faint keyboard sounds are me deleting that set of files for the old boards.

Well things may not be as bad as I feared. RTR12 just rebuilt his breadboard circuit to the exact same circuit as the board I built, and reports that it worked perfectly, including the use of extended BOD triggering.

So it seems that I may have a flakey component, perhaps the 556. Planning a bit more testing tomorrow including a new 556, and go from there. 

Rod

Interesting, I wonder what's different?

Different times set. If the trigger doesn’t go high 10 uS before the time is up...

They must be using different times.

GRJ & cjack, What's different is definitely the $64 question? We are trying to figure it out. Quite puzzling. 

I am using 1 meg pots only for the red and yellow timing. I don't have the fixed resistors installed as shown in the drawing. Rod has these on his PCB I believe, but I don't see how that could be a problem either way?

I've tried different values for each 1 Meg pot along with several timing combinations for red and yellow, each one longer, shorter, same, different block trigger times (with the push button) etc. and all seems well here so far. Tried activating the circuit when they yellow was on. I can't seem to duplicate the problem?

The only quirk I have is when first powering up the bread board, without activating the block detector switch, the yellow comes on for a short time and then switches to green (default state) as it should be with no block activation. It then waits patiently for the block activation switch to close. Seems like this has happened in a few of the circuits we have tried for this project. I suspect this would probably not be noticeable when one was first powering up their layout. 

cjack posted:

Different times set. If the trigger doesn’t go high 10 uS before the time is up...

They must be using different times.

Microseconds? 

It's just that the trigger has to be shorter (by 10 microseconds) than the monostable time or the output will remain high until the trigger goes back high. And I thought that the setting differences and block signal time between the two boards tested might by why only one seems to work.

I'm confused about D2. What is it for?

Good question on D2. Rod might be able to provide a better explanation? But, as far as I know D2 was on the original schematics when we started trying these circuits and was just left in place. It was labeled 'Negative Recovery'?  Honestly, I never thought to remove D2 to see what happened, but you have now given me the idea to give that a try. 

I've tried several times today to make this circuit fail and so far it still works fine no matter what I do. Earlier, I accidentally turned the red timer pot (multi turn trimmer) down too far and got some odd results. Thought I had broken the pot or shorted something out? Checked and the pot set to 0.1 ohms. Reset to around 100k and all was well again.

I am using a bread board with 1 meg pots only, no low limit resistors installed ahead of the pot as shown on the schematic. I believe Rod does have the 200k minimum resistor installed. He's using a PCB made from the schematic. 

Well the beat goes on, but no resolution. I swapped in a new 556 but it behaves about the same way. And it is not consistent. Mostly it works as it should. But on occasion when the BOD is jumpered the green led stays on, it does not go to red. Then perhaps after 15 or 20 seconds, with nothing else going on, it will switch to red, and then after the BOD is opened it will time out normally.

Today I am going to build up a new board and see what it does. I must have a flakey component or connection on this board, and it's just faster to build a new one. If the new one works properly, guess where this one is going to wind up? Haha. I am also communicating with Rob Paisley and I plan to ask him what the negative recovery diode D2 actually does.  I have not seen anything like that on any other 555 or 556 schematic, or in any datasheets. In response to my first email to Rob 2 days ago his first question was; is D2 installed, and is its polarity correct.

Rod

cjack, I just did some experimenting with D2 and it does seem to serve a purpose in the circuit. 

With D2 in circuit you can hold the block detection contact closed as long as you want. When released the red then goes through it's complete cycle, then yellow cycles, then green.

With D2 removed, a momentary contact closure of the block detection device results in a normal cycle, red, yellow, green. But, if you hold the block detection contact closed longer than the red's timing cycle, when block detection contact is opened it goes immediately to the yellow cycle and then to green when the yellow cycle completes.

So, with D2 removed from the circuit, depending on how long the block detection contact is closed, the red cycle is either shortened or eliminated after the block detection device's contact opens.

Hope that makes sense...

Thanks I see that now with your explanation. The diode holds the DSC input low so that the 556 can't time out.

Rod Stewart posted:

Well the beat goes on, but no resolution. I swapped in a new 556 but it behaves about the same way. And it is not consistent. Mostly it works as it should. But on occasion when the BOD is jumpered the green led stays on, it does not go to red. Then perhaps after 15 or 20 seconds, with nothing else going on, it will switch to red, and then after the BOD is opened it will time out normally.

Today I am going to build up a new board and see what it does. I must have a flakey component or connection on this board, and it's just faster to build a new one. If the new one works properly, guess where this one is going to wind up? Haha. I am also communicating with Rob Paisley and I plan to ask him what the negative recovery diode D2 actually does.  I have not seen anything like that on any other 555 or 556 schematic, or in any datasheets. In response to my first email to Rob 2 days ago his first question was; is D2 installed, and is its polarity correct.

Rod

Maybe you could post a hi res picture of the built up board and other eyes could check it out for accuracy. Might help.

Regarding the latest schematic in this thread:

1) The output of the bridge rectifier directly supplies the 555 timer IC supply voltage (in orange).  If you supply 16V AC, that will generate over 20V DC at the IC chip which exceeds its operating voltage range.  I suggest you power the IC from the 8V DC 7808 output.

2) The "reset" inputs to both 555 timers is shown as No-Connect in this version of the schematic (they were connected to the supply voltage (as it should be) in at least one previous schematic you posted.

A floating or disconnected Reset input can cause flakey unexpected behaviors.  I also notice earlier schematics show the LM556 bipolar version of the dual 555 while the most recent schematic shows the lower-power TS556 CMOS version.  For example, regarding the typical Reset current the CMOS version requires only 10 picoAmps (typical) to trigger and inhibit any timer operation.  That's >10,000 times less current than the 0.1 milliAmps for the bipolar version. You can just about generate 10 picoAmps by staring intently at a circuit!   In other words, connect the Reset pins to the supply voltage!

stan2004 posted:

You can just about generate 10 picoAmps by staring intently at a circuit!   In other words, connect the Reset pins to the supply voltage!

That brought a smile to my face!

Actually I HAVE been staring intently at the whole mess over the last few days! Haha. VERY intently.

Stan, point taken on connecting the resets to Vcc; that was my next plan of attack. Since my last post I have made a couple of discoveries. For my second board build I left the C1 filter cap out of the circuit, since for test purposes I was only planning on using a DC supply. It was operating pretty well, no funny stuff. So I stuck C1 in, and guess what? Everything went sideways. It started behaving similarly to the first board; not triggering sometimes, and triggering itself sometimes. Really weird stuff. RTR12 tried using a 220 mike cap in the supply to his BB circuit, and also got some weird unpredictable stuff happening.

I did not realize that the cmos version 556 chips were that much more  sensitive; that does explain a lot. I thought all along that a 556 was really just two 555's in the same chip. Pics below of #2 build. Now to be clear, this is an earlier version (R5.3a) than version R5.51 originally uploaded in this topic. Reason being these were the first boards I ordered, and the first I have received. This early version uses only two transistors, and one or two diodes. But the front end of the circuit, the timing part, is identical to the later version, except there is no TO-220 reg.

Good catch on the U1 power connections also Stan. I missed that. That was supposed to be connected to the Pos rail after the reg. Another change for the next set of gerber files!

Research continues, Rod

Well after adding the Vcc to reset pin jumpers as Stan suggested, I am pleased to report that both the boards I have built are working just fine, with no erratic behavior at all. So based on an example of two, all seems good. It turns out that adding the jumpers to the 556 socket is very fast and easy to do from the underside of the boards of course, so no big deal. RTR12 is also doing independent testing on his breadboard circuit of the same schematic, so hopefully he will confirm the results. So if all goes well with the collective results, we should be able to make revisions to the gerber files and repost them here to replace the earlier version. As always, this has been a good collective effort with input from many who are wiser than I, and hopefully the final result will be something worthwhile. Stay tuned. 

Cheers,

Rod

I guess that means that Stan was right, just looking at it was enough to upset the applecart!

What's the unusual positioning of D3 all about? 

Some of the circuits we tried needed 2 diodes in the green cathode wire back to the 556 for it to turn off completely. I think Rod put provisions on the PCB for two diodes just in case. He only needed one diode most of the time, I think he only had the green problem a time or two. I had the problem almost all of the time here and needed the 2 diodes. We also have different 556s, as Stan noted above, if that could cause a difference? Rod has the ones you can stare at to trigger, I have the others. 

I suspect the CMOS version has outputs that are closer to the rail, which would account for differences in operation.

One good reason for always having a regulator on the power supply is you get more consistent operation.  If you're running a variable voltage input to the circuit, you have an infinite set of possibilities for voltage thresholds.

So we have come up with a new version of the circuit for this board, that has some nice upgrades going for it. Posted below.

It includes provision for a TO-220 regulator as before, jumper selectable, and the Vcc supply to the 556 chip is now from the regulator output, after several folks suggested this. It still includes provision for both a N.O. block switch, as well as an opto-isolator input. I have added a second pot for those who want an adjustable yellow time delay as well as the red. Another nice adder is the circuitry between the two 556 halves comprised of Q1, D4, C4 and R8/9 controlling U1.2 reset. This was suggested by Rob Paisley of Circuitous, and it cancels the yellow signal whenever the block is re-triggered. Previously when the block was re-triggered part way through the yellow time delay, the yellow would stay lit until it timed out, even though the red led was lit. This addition prevents that. Also connecting U1.1 reset to Vcc prevents false triggering which was causing all sorts of grief before. And as before it easily converts to 2 aspect activation by subbing a 1N4148 diode for the R6 pot.

Both RTR12 and I have tested this circuit extensively over the last few days and we are pretty happy with the way it works, and it is very stable. So unless anyone sees anything amiss I will probably post the new build files, BOM, and gerbers sometime in the next day or two. I have ordered some boards already but as before they won't be here for a couple of weeks. So you are cautioned that this circuit has been breadboard tested only!

Rod

Rod, do you have the DipTrace files for this version?

OK so here is a couple of views of the revised board, and the gerber files for those who wish to order some boards. These go with the circuit 2 posts up. The BOM is also posted for both onshore and offshore parts sourcing, and the User Notes are included. Feel free to ask any questions.

Rod

I don't know if anyone on the forum has ordered these boards or built any; but I am happy to advise that I have done a test build and they work exactly as intended. They are quite stable now with no unintended trips or resets. Also the yellow cancelling when another train enters the block works exactly as it should. All the files posted immediately above are current; I have added an updated set of User Notes that contains a couple of edits and an expanded description of operation. 

Rod