GMC
I've been on vacation.... Did you build it ok?
HEY ronv... how ya doing my friend.... I got the 555 working fine, perfect 50% duty and right rate (had to add a diode). This picture shows both Left and Right Channels flashing alternating at about 90 fpm or 1.5 Hz kind of slow for an analog scope so I had to turn out the light and rely on the persistence of the CRT on the Tek 2235A to show the nice pattern. I made some simple RC flip flops that worked well but the pattern was not even close as sharp as these. They were very ugly
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**broken link removed** (don't laugh I used my old Science Fair for protoboarding)
Then I chucked it all. I went off into PICAXE land. Still using a lot of your great help and ideas, thanks again. The switch to a PICAXE simplifies switching, increased capabilities and flexibility and can be customized easier, just going to the microprocessor. I went with PICAXE for prototyping, may be low "production". There are better cheaper micros but this was easy to get into with the free simulator programs and compiler. $3.50 per chip (plus $1.00 for a voltage regulator) verses $0.50 for a 555 is more cost. Still it is slick. Basic is easy to work with. I brushed off my programing skills and made some nice code that runs very efficiently. I can program any flash rate or patterns I want. I can even have a few to select from based on non volatile memory that the user can configure. With some clever "switch logic" and programing, the user can configure a few light patterns in the second flash pattern (if one wants to use two different wig wag patterns, it's optional). There is non volatile memory in the PICAXE that you can read or write on with the code. With some a switch throw during power up, with in an allotted time, a few seconds. I might put a seperate program button on the box. WAY OVER KILL FROM THE ORIGINAL 555.
I have it designed around a single 5 or 6 position, 3 pole rotary switch, selecting: Off, L, R, Both, Flash, Flash (2nd bonus pattern anything I want and can be configured to some preset patterns). I could use a single three position toggle, off-both-flash to access less functions. I could use two toggles to get more functions. The rotary is the easy way to get all the functions in one switch, but the user is not limited. I didn't want any button pushing to CYCLE through patterns, which I could have done, but I want simple SWITCH POSITION showing what function you are on.... no guessing. That is the way planes are, switch position is the setting, no ambiguity. With the micro processor, I set the switch logic to be open (off) and ground on (pulling a high to a low on the PICAXE). The code looks for the voltage on the switch channels. There are 5 I/O channels to the IC processor. I am using 3 as input, two as output. There is also a serial interface and power making up the -08 Picaxe.
I have the chip working and programed. I need to get the power transistors along with all the mechanical stuff, packaging, case, connectors, heat sink and making the final board. That will be easy. I am using a PCB that matches the PCB, so it will be a direct duplicate. I am not going to do a custom board and have them made, yet. If I want to make a bunch I might, but the prototype now. PCB Breadboards with a few jumpers still makes for a clean nice board. The wiring turned out to be easy. It is deciding if I want to use a terminal strip, Molex, wires with Fast-on connectors and the case and mounting of the board and heatsink that has been the time consuming part.
I have put it on the back burner for other projects. I have a Mouser order about to go in to make the final prototype.
I upgraded the FQP27P06 MOSFETS. The ones I am going to get handle more amps (FQP47P06 or STP60NE06L-16) and make less heat. Even though I only have 4.5 amps to switch I wanted it to be able to handle more, with some head room. They also run a little cooler (Rthj-case of 0.94 vs 1.24 Celsius/Watt). Since I using them for steady current as well as flashing, a small heat sink with passive cooling will be needed to keep it from getting too hot. I don't remember but it was approx +2.5 watts to dissipate. The case is aluminum and the power transistors will be thermally attached to the box as part of the cooling, but an additional small internal heatsinks will be added as well, all electrical isolated from the case of course. I am trying to keep the temp rise under 60F. It will need to have some vents in the case as well.
Having fun. I will post the final product. Here is a rough draft. I have changed it a lot since. The power transistors need to go near edge of board to mount on case. Again the biggest part is packaging it.
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