I found it. There were actually two version posted, this one gives an explanation of how and why it works, vs the other oen which was just a schematic and woudl be meaningless to someone who wasn;t familiar with the 1802 CPU chip.
Note the current draw - 2ma! A pair of AA batteries would run that for years, 24/7. This is why that particular CPU was popular for spacecraft duties. LOW power.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
CSX Robertrrinker The insane geek method - find an old RCA 1802 microprocessor (yes, a complete 40 pin microprocessor to make a simple LED flasher...). You wire some of the address and data lines together to hard wire in a program, and it makes an LED flash... I know this is waaaaay off topic, but this would not work as stated. You can not hard wire in a program buy tying some of the address and data lines together. The chip reads the program by changing the address lines and reading the data lines, so you have to interface it to a memory chip or use a LOT of logic gates.
rrinker The insane geek method - find an old RCA 1802 microprocessor (yes, a complete 40 pin microprocessor to make a simple LED flasher...). You wire some of the address and data lines together to hard wire in a program, and it makes an LED flash...
The insane geek method - find an old RCA 1802 microprocessor (yes, a complete 40 pin microprocessor to make a simple LED flasher...). You wire some of the address and data lines together to hard wire in a program, and it makes an LED flash...
Actually, you CAN - one of the little beauties of the 1802. There is a way to hard wire a simple program into the chip and an LED will flash. I know the description of exactly what you need to do is out there, unfortunately it's on the Yahoo 1802 group and the search there never returns the same results twice. It works on the 1802 because of the ways certain pins are shared. It gets put in a looping state with atleast one pin alternating high and low. I don't know that it is actually possible with any other 8-bit CPU, but it definitely is with the 1802. An 1802 system was my very first computer, back in 1980 - and sadly it has become a forgotten footnote - even though at least two of them are operating still in the Voyager probes.
Edit: I posted to the group hoping either the original poster or one of the otehrs will rememebr and link me the schematic. Also, this whoel thign is possible because the 1802 is a CMOS device and can clock down to 0 Hz - if you build such an animal with a more typical 1.7xxxx MHz clock, the LED will flash far too fast - you have to also slow the clock down so the state changes take longer.
Renegade1c One of the coolest FRED I saw was actually a truck that picks up power from the track and has a surface mount LED attached to a kadee coupler that you install into the pocket of the car and simply replace the whole truck. I know Caboose Hobbies here in Denver has it. it requires no battery and its rate is constant. Also all the electronics are built right into the truck, so problems hiding it somewhere in the car. Just an alternative to consider. I was the nicest FRED I have seen to date.
One of the coolest FRED I saw was actually a truck that picks up power from the track and has a surface mount LED attached to a kadee coupler that you install into the pocket of the car and simply replace the whole truck. I know Caboose Hobbies here in Denver has it. it requires no battery and its rate is constant. Also all the electronics are built right into the truck, so problems hiding it somewhere in the car.
Just an alternative to consider. I was the nicest FRED I have seen to date.
It has been mentioned already... :
jasperofzealThe easiest would be to get a EOT from Ring Engineering (on sale at Walthers). These EOTs look good and are DCC compatible out the package. I don't have one to tell you how it works (maybe someone here does), but they sure look nice and may be worth the price.
TONY
"If we never take the time, how can we ever have the time." - Merovingian (Matrix Reloaded)
Colorado Front Range Railroad: http://www.coloradofrontrangerr.com/
A 3mm LED is almost an HO scale foot, it wouldn't look too good.
jeffrey-wimberly One way could be to rig a car with wheel pickups connected to an old Digitrax FX3 decoder. Set the headlight function to 9 (end of train light).
One way could be to rig a car with wheel pickups connected to an old Digitrax FX3 decoder. Set the headlight function to 9 (end of train light).
This is not a bad idea and for the price for one of these 1 function decoders, it rivals the price of other EOT devices. Thanks for giving me something to consider for myself, Jeffrey.
Digitrax function decoder
The simplest possible FRED is to use a Flashing LED. The only other components necessary are a battery, resistor, and on/off switch.
All Electronics sells flashing LEDs that operate on 3-5 VDC as their product numbers LED-4 or LED-72R in sizes 5 and 3 mm, respectively, for less than $1. Shipping is the killer unless you need other items from them.
The insane geek method - find an old RCA 1802 microprocessor (yes, a complete 40 pin microprocessor to make a simple LED flasher...). You wire some of the address and data lines together to hard wire in a program, and it makes an LED flash. The geek factor here is that it draws LESS POWER then the old LM3909 LED flasher chip. The downside, the enthusiast community for these chips, which is quite rare these days, would not be happy that one was dedicated to such a mundane function. My bery first computer used one of these chips, and I still have it, and it still works. Some other famous uses for them, which you may have heard of - the Voyager spacecraft (which are STILL WORKING!), some of the Mariner probes, and even the Hubble telecope (although I think an 'upgrade' done to the Hubble a few years back repalced the original CPU package with a much faster and a little more up to date 486 based system..).
Dr. Frankendiesel aka Scott Running BearSpace Mouse for president!15 year veteran fire fighterCollector of Apple //e'sRunning Bear EnterprisesHistory Channel Club life member.beatus homo qui invenit sapientiam
Here are some links concerning the Ring Engineering EOT. I was not aware of this product until now.
http://search.yahoo.com/search?p=Ring+Engineering+eot&fr=yfp-t-501&toggle=1&cop=mss&ei=UTF-8
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
As previously stated, the LM3909 IC chip is discontinued and hard to come by. It was highly used to make FREDs back in the day, here is the LM3909 circuit in case you find one. Another IC that was pretty good for FREDs is the Holtek Devices HT-2014 chip. It was a smaller package (TO92) compared to the LM3909 (8-pin DIP) and required only a resistor for the LED chip as opposed to a resistor and capacitor for the LM3909. Here is the circuit for the HT-2014, again, the chip is also discontinued but can probably be found somewhere.
Your options now are to buy ready-made circuits to simulate FREDs. I like this one from Ngineering, N8040. It's small so it can fit pretty much anywhere and can be powered throught the track or with a battery. Read the info to get all the details. You'll need a FRED installed on your coupler, so maybe using the Details West ET-227 would be appropriate. Other manufacturers offer FRED simulators, so you have many to choose from.
The easiest would be to get a EOT from Ring Engineering (on sale at Walthers). These EOTs look good and are DCC compatible out the package. I don't have one to tell you how it works (maybe someone here does), but they sure look nice and may be worth the price. Good luck with what you choose.
The LM3909 was discontinued some years ago. Might find it on a surplus list somewhere.
http://search.yahoo.com/search;_ylt=A0geu.MXXQNJgI0ARMdXNyoA?p=lm3909+discontinued&y=Search&fr=yfp-t-501&ei=UTF-8
One I've been using for years is a simple circuit that was published in Model Railroader January 1986 issue. It uses an IC type LM3909, which is called an "LED Flasher." All you need to add is the battery, capacitor to determine flash rate, and an on-off switch, plus, of course, an LED(s).
LM3909 IC
220 ufd 16 Volt Capacitor
AA or N Battery
LED(s)
Small on-off switch
The LED connects across pins 6 (anode) and pin 8 of the IC.Pin 8 is shorted to pin 1. The capacitor is tied across Pin 2 (+) and pin 1. The battery is tied across pins 5(+) and 4, with the switch in the battery circuit.
I've found the shelf life of the battery is more an issue than the type, I use a good alkaline battery and these things last for years. A rechargable battery, run on the track circuit seems to be a lot more trouble than it's worth. It also goes against the K.I.S.S. principle. I even have them installed on my double stack cars (circuit and battery hidden under the bottom container with the switch sticking through the top, just lift off the top container to turn it on or off), and on my spine cars (circuit and battery hidden in the trailer with sockets and pins going down through the wheels to the LED mounted above the coupler.
http://www.awrr.com/FRED.html
http://www.google.com/search?hl=en&q=FLASHING+REAR-END+DEVICE&btnG=Search
I was just wondering if anyone had a diagram and a parts needed list for making your own flashing rear end devices, or if you know where to get some at a reasonable price. I would prefer battery operated but welcome what ever you have info on.
Thanks Dusty