# looking for Circuit Design help

#### bountyhunter

Joined Sep 7, 2009
2,512
Hello

I tried a search first but could find nothing to match my needs.

I would like to build a dark activated LED; Red, Green or bright white. It would be used for buoys for R.C Boat runs, so they would be in water.

I would like a circuit that would allow me to set the LED to flash and I set the rate OR leave them on constantly until light. It would work off of either a 9v or 2 C cells (good ballast weight).

Any help would be appreciated and I need the circuit to be as physically small in size to fit in the to be build bouys.

George
With 2C cells, your end of life voltage is about 2V. I would build a flasher using a CMOS 555 timer that runs down to about 1.5V driving the LED.

#### bountyhunter

Joined Sep 7, 2009
2,512
Hi BUT I also wanted a dark sensor to activate this for night use
I'd get an ultra low quiescent current op amp with a photo sensor that drives a P-FET to turn the power on and off to the flasher.

#### tracecom

Joined Apr 16, 2010
3,944
Hi Mr. Bernard

Thanks for the fast reply. Just a couple questions after looking at your circuit.
SW1 is that a two position switch, could I use a two position toggle switch there? Also the transistor is that a BS170 / NTE490 and R2 is the adjustable LED flash rate? How do I switch from the LED flashing to being on continuously?

Sorry about bothering you with these questions, just want to make sure I understand it. Also Thanks for your help.

George
SW1 is used to select whether the LED is on continuously or flashing; yes, you can use a SPST switch. The transistor is an N channel MOSFET: BS170. R2 adjusts the flash rate from about 1 flash per second to faster than the eye can discern. To turn the circuit completely off, disconnect the battery, or add another switch. Bernard suggested a ball switch, so to turn the circuit off, turn the buoy upside down.

The schematic needs to have pin 8 labeled (although it's the only one that is not labeled, so it's obvious that it is 8.) And you may need a pot to adjust the LDR for varying light conditions. Don't overlook the fact that the 555 is a CMOS version, not a standard NE555.

It works great.

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#### Wendy

Joined Mar 24, 2008
21,914
Hi Mr. Marsden

Could you please explain the switches? S2 makes the LED stay on constantly BUT I am a little confused by S1 - Sensor Off, OFF, daylight Sensor ??

Not sure what that means? What turns the circuit OFF , ON so the LED Flashes etc ??? What changes are needed for a Regular Green LED and a bright white LED ?

Sorry to bother you again with this.

George
Sensor Off means it will flash no matter what (the daylight sensor is disabled), Off is self explanatory, and Daylight Sensor will turn the flasher off during daylight.

S2 turns the LED on continuously.

Thinking about it I could have used the original schematic and added S2 in a different way to turn it off. Oh well.

#### george0039

Joined Oct 15, 2008
158
Hello Again

Thank You tracecom and Mr. Marsden for ALL your Time and Help.

I will be making a shopping list tonight and see about putting together each circuit to run them.

Thanks Again to both of you for your help and Patience!

George

P.S Mr. Marsden are you aware that when I try to post something new I get the site go into limbo Or HTTP 500 Internal Server Error, Two days now ???

#### george0039

Joined Oct 15, 2008
158
Hi tracecom

In your circuit picture, could you tell me where you got that power circuit board attachment for your protoboard, that makes life very easy to power experiments.

George

#### tracecom

Joined Apr 16, 2010
3,944
Hi tracecom

In your circuit picture, could you tell me where you got that power circuit board attachment for your protoboard, that makes life very easy to power experiments.

George
That is my own design (with the help of some AAC members.) I have built up three so far, one for 5V, one for 9V, and one for 12V. I like to use a solderless breadboard, so I have several pre-configured assemblies that fit into solderless breadboards and save my assembly time. Notice the little slide switch in my photo; it is mounted to a tiny PCB that plugs directly into the breadboard.

#### george0039

Joined Oct 15, 2008
158
Hi

That is sweat! Any chance you would sell a circuit board? I can solder the parts on myself.

George

#### george0039

Joined Oct 15, 2008
158
To: Blueroomelectronics

Reg. your post #25. You gave me something to think about and now for you. Would you be willing to help me with my circuit design and your pic? I dont know anything about pic programming so could you supply the programmed pic?

Would it be better to go through here or private?

George

#### Bernard

Joined Aug 7, 2008
5,335
Thanks, tracecom, I relooked at the circuit and did not see any skipped lables. That is a novel use of pin 5 for light-dark control; what works-works.

#### blueroomelectronics

Joined Jul 22, 2007
1,757
To: Blueroomelectronics

Reg. your post #25. You gave me something to think about and now for you. Would you be willing to help me with my circuit design and your pic? I dont know anything about pic programming so could you supply the programmed pic?

Would it be better to go through here or private?

George
The software and schematic is trivial for the button / LED only version, the only difference with different LEDs is the current limiting resistor. PICs unlike 555's don't like more than 6V so it would have to be a 4x AA or AAA to keep it nice and simple.

If you want PCBs you're opening up a different kettle of fish. I was assuming you were just going to solder the parts and wire them by hand on a perf-board.

I'll say it again, the costs are going to add up pretty quickly. How many do you plan to build?

#### george0039

Joined Oct 15, 2008
158
Hi Bill

Sorry about the misunderstanding. Yes I plan on soldering the pic to a experimentors board and wire/solder the other parts to it. As for voltage, if I can get good run life from it, I will try the other voltage levels.

I need for now a drawn circuit showing all the parts and connections and a programmed pic to do what I was looking for.

1. Using LDR, at night turn circuit on, daylight off
2. Selector switch to either Flash LED Red OR Continuous on ( can flash
3. Manual power off switch also to shut off entire circuit

4. I need the same functional circuit for a seperate Green LED
and a Seperate bright white LED

ALL LED used are Basic Models

Can you help me with this ?

George

#### george0039

Joined Oct 15, 2008
158
Hi Bernard

From your circuit posted in #56, R2 the 1mohm pot, looks like both outer leads are in the circuit but then it is not a variable resistor, should it be one end and the center wiper leads that are in the circuit. If so, what should the resistance value of that be tuned to so it does not hurt the I.C?

George

P.S I have ALL the parts in from your circuit and ready to get at it. What colour LED did you use with the 220ohm protection resistor?

#### Bernard

Joined Aug 7, 2008
5,335
Putting an arrow thru just about any thing makes it variable. R2 uses wiper & one end. LED is semi-bright RED with unknown specs, Vf 2.1V @ 30mA. The NTE 490 is almost same as BS 170. With pin 7 not used, there is no minimum R2 that will cause damage to IC, R1 just sets a max. flash rate & could be eliminated. As tracecom, suggested, R3 could be variable, maybe a 250K to 1M pot

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#### Bernard

Joined Aug 7, 2008
5,335
How are you getting 360 deg coverage, multiple LED's?? Do you have the LED's & specs.? What does buoy look like?

#### george0039

Joined Oct 15, 2008
158
Hi Bernard

For my bouy project I just picked a basic Green LED and a basic Red LED and a bright White LED. I might go with 5mm for size. I NEVER thought about 360 deg. ?? As for bouy plans, I went on line to see what Canada and the U.S are using for channel markers, NOT that I am a sailor and wood know. The design is what looks good and has the LED on the top and the electronics in the lower body with the battery and ballast weight.

As soon as I get one proto board circuit running I will post it here after I first ask you how that is done. Not now but when Im ready, dont want to bother you now.

Thanks

George

#### SgtWookie

Joined Jul 17, 2007
22,210
"Top hat" type LEDs are designed for 360° viewing; however much of the light is simply radiated upwards. Most LEDs you see online (particularly on auction sites) have a very narrow viewing angle (20° to 30°) in order to artificially inflate the brightness specification; of course you can hardly see them at all outside this angle. Solar-powered garden lights use a mirrored inverted cone to spread the light in a circle.

If you want to emulate actual bouys in use, here:
http://www.sailingissues.com/navcourse9.html
is a page that will help you decipher bouy markings on nautical charts for better accuracy. The flash patterns of real bouys are fairly unique to better assist in navigation; as it's important to not only know that you are within the channel, but WHERE you are in the channel.

Replicating a particular bouy pattern could be rather parts-intensive without using a microcontroller. However, there's a design using a couple of 4000-series ICs that can be "programmed" on-the-fly for various flash patterns (or steady-state) - but it would need the day/night function added on.

Four AA cells are far superior to one 9v battery. If you have tight space restraints, go with four AAA's instead. A 9v battery should be considered a "last resort", as they are very expensive in comparison, and simply don't last very long. A 9v alkaline battery might be rated for 500mAh, whereas an AA alkaline would exceed 2000mAh - over 4x the capacity.

Bernard, you're right in that the CMOS 555 has a limited current SOURCE ability (10mA) from the output pin 3 - however, it can SINK up to 100mA. With that in mind, you could sink current from the LED instead of sourcing current to it, and swap the timing components around to achieve the same result without requiring the BS170 or equivalent.

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#### Bernard

Joined Aug 7, 2008
5,335
As The Sgt. said, we can drop the BS 170, & connect pin 3 to LED cathode.

#### george0039

Joined Oct 15, 2008
158
Hi Bernard

Can you please confirm something for me? If I understand your last post, I dont need the BS170, I can connect the cathode of the LED to pin 3 and I still can use 9v OR do I only use 3-AAAs or is it 4 -AAAs?

The Rest of the circuit stays the same?

As for type of LED used, during the day I just figured I would paint the top portion of my bouys Red, Green and at night an average Red, Green, White should be pretty visible.

Im not going for authentic but something that looks good enough for R.C boat use.