Semaphore and 555 Timer Circuit

Oops.  There is a problem with my recommended inverting circuit.  

I thought I was saving you a resistor per inverter-buffer by using a FET.  But this only works if directly driven by a digital gate like the CD4017.  Instead, in this design there are diodes in the path.  So bottom line is you do need a resistor paired with each transistor when you use an N-FET or an NPN.  It's just the resistor is hooked up different depending on the method.  Sorry for the misdirection.

For driving a few LEDs per transistor as in this case, either method works equally well.  If you were going to drive heavier loads I'd suggest the FET method which is more efficient albeit a few cents more per buffer. 

Thanks Stan,

Just printed out your drawings above and was studying them to modify my wiring diagrams. I'll still be using the FETs when they arrive and the added resistor isn't a problem, but thanks for catching that. I'm sure I would not have noticed until something went wrong somewhere. But, I always order extra components just in case of any unintended smoke releases that may arise. So far so good though, no smoke! I will post back with my results, or maybe more questions first.

Stan, I think I may have it re-worked with the BC547s (MOSFETs next). Here's the revised schematic, if I got everything in the proper place (including the wires). I couldn't get the transistor symbol to cooperate as far as orientation goes, so I changed the CBE designations to match your examples.  And as usual, any further input welcome (and wanted ). 

If I got this correct, that really reduced the output wiring. Makes me feel like I missed something...

 

 

Curious your choice to use two 6-pin connectors, and two 2-pin connectors for the 16 total connections.  This means you're doubling up on the common wires - N-S common and E-W common have 2 wires to each PCB terminal.  I'm not saying this is wrong or won't work - but perhaps unconventional.

It just seems you have 4-wires coming from each wehonest signal head and IMO you'd want those 4-wires going to a single 4-terminal connector on the board.  I don't know if there are economical 2mm pitch screw-terminals available but on eBay you can get 2.54mm (0.1") 4-pole screw terminals for 40 cents each from a US seller...a little cheaper if you can wait for Asia.

I don't know the gauge of wiring coming from the signal heads.  Screw terminals like this don't like really fine wires in terms of clamping down to make a reliable connection...but you can always "fold" the stripped wire ends back on itself to essentially double up the diameter of the wire to give more clamping area.

Thanks again Stan, I see my error now that you have pointed it out. I guess it was old thinking carried over from the previous circuit. Back to the drawing board. Let me try this again and I will repost. The terminals you listed also look good, that's a good price compared to Digikey. I better order a few!

I'd jump right to the FET's, they'll do all you want to do and aren't any more complicated to wire in than the transistors.

I do plan to use the FETs, but they are still on order and I don't have them yet.  I was only going to try this out with the transistors I do have on hand and then swap them out to the FETs when they arrive. Was thinking it shouldn't be too hard to swap them out and redo the circuit once I had the basic stuff in place. I won't be trying any PCBs until I get the FETs. And the way things are going today, it'll probably take me until the FETs arrive to get it working...it also keeps me busy and off the streets! 

You're too easy, it takes a bit more to keep me off the streets.

I'm easy, but I ain't cheap!    Some slacking in old age is a big factor too. 

I think I have the corrections made, time for a look to see what I have screwed up this time (before posting). Whatever it is, I'll probably miss it again though...

Ok, I have another schematic to look at. I got myself confused a few times re-doing this (sometimes that's pretty easy for me). Hopefully it isn't too far off this time and I'm at least getting closer.  

Looks good by me.  

Not that you'd be using MTH signal heads...but wouldn't it be dandy if you could plug their 4-wire cable right into your board.   Not sure if they use common-anode or common-cathode, not sure exactly what kind of connector they use, not clear how their wire-color-key maps to the LED colors, etc..

Thanks Stan! I even have it working on a breadboard too. Once you get all the little jumpers plugged into the correct holes in the breadboard it works great. Someone had a couple wires in the wrong breadboard holes right out of the gate, but they found and corrected them and all is well now. 

Still haven't found my We_Honest signals, all I can find are some red & green 2 LED signals that I have for switch indication. However, I am sure I do have a set of the MTH traffic signals you mention above and I'll dig those out and see how they could possibly fit together. I like the 'just plug it in' idea. 

I have been fiddling with the trimmer pot and capacitor values and I thin with the 220uf cap a 50k pot is more than sufficient. At about 25k ohms on the pot you get about 40 seconds on the red and green and 10 sec on the yellow. Have also been trying to tidy up my drawing and turn it into a PCB. Using Diptrace is quite fun and really not too hard to learn enough to get started with it. I still have a lot to learn though.

MOSFETs should be here by mid-week.

Thanks for all your help!

Here's the schematic for the MOSFETs, hopefully all the wires connected correctly as I ordered some PCBs from JLCPCB for both the transistor and MOSFET versions. As an FYI, it was $2 for the first order of 5 (transistors), then $4 for the next 5 (MOSFETs) and $5.91 for shipping. Not too bad on the pricing. Due to the larger size than I have ever had before, OSHPark was $26.50 for 3 PCBs shipped. I can see clearly now what GRJ was talking about with the PCB size being a big factor on where to order your PCBs.

The plan is to assemble one of each PCB to make sure they work properly, then post all the Gerber and drawing files along with a materials list (Digikey part numbers included) for anyone that might want to make some of these for as a hobby project. With the Digikey part info you could most likely find the same items on ebay from Asia and possibly save some on the parts order.

Stan, I can't find my MTH signals either, I think I am missing a box of stuff somewhere? I probably put them in a 'safe' place somewhere... I'll keep looking, they should turn up one of these days? When found, I'll see about making the connections for them and a PCB to match and report back. And also a big Thank You for the assistance and the revised 4 wire design to make this work with some of the readily available traffic signals. 

 

   I didn't look to see exactly how the applies, But CBE postions on a component should'nt be taken for granted. I've ad suppliers throw curveball odd numbering additions into normal packaging needing two legs cossed and/or reverse placement. Read the included data sheets every time .

Adriatic posted:

   I didn't look to see exactly how the applies, But CBE postions on a component should'nt be taken for granted. I've ad suppliers throw curveball odd numbering additions into normal packaging needing two legs cossed and/or reverse placement. Read the included data sheets every time .

Back in the day, Radio Shack would sell a grab-bag of random and cryptically marked transistors. No data sheets included.  But a hobbyist willing to spend the time could save some money sorting through these.  While I can't imagine anyone doing this today, I see that the "FREE with coupon" Harbor Freight DMM still offers the so-called hFE transistor-test function which allows you, in effect, to determine the CBE orientation of a transistor as well as its polarity (NPN vs. PNP).  Here's the meter set to hFE mode with an NPN with the EBC orientation showing an hFE (current gain) of ~200.

Unfortunately, this is NOT suitable for working with FETs.

 

 

I probably should have waited for the MOSFETS to arrive, they are still not here and the ebay listing said guaranteed delivery by June, 26th. So much for the 'guaranteed' delivery date. 

I bought a kit on ebay and built one of the 'transistor testers' which has worked pretty well so far. They are pretty inexpensive and can be found lots of places. Since I don't know the resistor color codes, that's how I check all my resistors to make sure I have the correct value. These are neat little devices, what will they think of next?  I find it to also be fun and relaxing!  

Of course that won't help my already ordered PCBs, if the actual part's don't match the schematic. Another problem with ordering on ebay is you don't always know what datasheet matches the part you are ordering. While Stan and others here can probably determine what they are getting, that can sometimes be a crap shoot for me. Keeping fingers crossed that everything matches up... 

This transistor tester looks identical to the one I have.

I could teach you the ditty that we learned when I was a kid to remember the resistor color codes, it goes something like "Bad Boys..."  I might get censured if I post the whole thing!

I've tried learning the colors a couple times, but never got there. (once when I was a lot younger too). I think I'm too old now...sleeping makes me forget what I had done the previous day. Like a reboot of the old PC, clears out all the memory.   Besides, I don't want you getting censured while trying to help out around here!     (Maybe I'll google it and see what comes up?)

Well I googled it and came up with John's version but also this sanitized one--

Bad Boys Race Our Young Girls But Violet Generally Wins

Better Be Right Or Your Great Big Plan Goes Wrong