Hi, I've just signed up the forum, as I'm a total newbie to electronics but thought I'd give it a go just for a hobbie. I set myself a little project, I bought a cool looking old aircraft indicator, hopefully I've managed to attach a picture of it, but basically it's 5 rows of 4 minature lightbulbs, midget flange ones, written on the side it says 28V .04A whihc im guessing are the lamps in there at the moment.

So far, I've managed to hook it to a Nano board and have programmed the lights to come on in sequence and jump about etc., I'm just playing aorund really, with a view of learning as I go.

My next question, if any one could help me is options to replacing the lamps. They are very dim at the moment due to the fact they are only being powered through the 5V nano board, so I wondered what I could replace them with, lower powered lamps, or LEDS, and as I'm running the 5V nano processor, will I be limited to using 5V for the whole circuit?



Sorry for the very basic questions, as I said I'm just learning really so apologies, any help or advice would be great.

Thanks

 

Not a good idea to power the lamps directly from a GPIO pin.

You could use a load driver chip in between the bulbs and the Nano such as the ULN2003 then power the bulbs at 12 or 24 volts.

If the bulbs use a standard “automotive” base you can find replacement LED types for them here that will run at 12 volts.

www.autolumination.com Automotive, Household, Truck Lighting Products Led Bulbs Wiring and Electronics (superlumination.com)

 

How many lamps are involved, (per legend) for example, you can get strip LEDs that may do it.

 

There are 4 lamps per legend or row; so 20 in total.

I've seen some LEDs that might work 3V ones I could just reaplce them with as I'd like to keep much of the inners as original as possible as its relaly well put toegther.

What I can't work out or have no idea about, and I need to learn, is how do you work out how much power is needed?

So if there are 20 Lamps in total do you have to have enough power to run them all and the processor, and how do you work that out? and the rating of the LEDs is that what's required to run them or the highest voltage they can take etc.

Sorry I said I was a total newbie, but I'm enjoying learning and appreciate the help!

Thanks!

 

You need a simple driver circuit for the LEDs which you drive from Nano.


or two in series if you have other than blue or white leds.

 

This is what I have at the moment - basic I know, but I'm happy with it. I've only left in 1 lamp in each row in case you were wondering, becasue they were so dim I could hardly see them. but I have no idea about powering it and what voltage LEDs or Lamps I should look for.

 

How many rows of 4 do you want to light up at any one time?

If you want all of the rows to be lit at once with the original bulbs you will need a 28 volt power supply capable of delivering about 1 amp.

Do the math for other numbers to be lit at one time.

 

Typical Arduino I/O pin can supply 40mA each with the entire board supplying 200mA. That is for the UNO so not sure of the Nano. I usually limit the pin load to ~20 mA or so not to overload it. Typical transistor switch most start with is the 2N2222A which can handle 40V, 0.8A, for a total of 0.5W. They are cheap and universally available. Usually plenty for beginners to play with. That is just for fun and giggles and can go up from there as needed with different components such a logic input MOSFET transistor or even a small 5V signal relay. Remember that LEDs are NOT voltage devices but depend on amperage. Find the PDF for what you are using but typical run of the mill, through hole, colored LEDs, typically have ~30-40 mA max so current limiting resistors are used to protect them from burnout. Once again I limit them to ~20 mA which is plenty bright and gives longevity.

Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view

And Welcome to AAC!

 

Typical Arduino I/O pin can supply 40mA each with the entire board supplying 200mA. That is for the UNO so not sure of the Nano. I usually limit the pin load to ~20 mA or so not to overload it. Typical transistor switch most start with is the 2N2222A which can handle 40V, 0.8A, for a total of 0.5W. They are cheap and universally available. Usually plenty for beginners to play with. That is just for fun and giggles and can go up from there as needed with different components such a logic input MOSFET transistor or even a small 5V signal relay. Remember that LEDs are NOT voltage devices but depend on amperage. Find the PDF for what you are using but typical run of the mill, through hole, colored LEDs, typically have ~30-40 mA max so current limiting resistors are used to protect them from burnout. Once again I limit them to ~20 mA which is plenty bright and gives longevity.

Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view

And Welcome to AAC!

Thank you! Sam alot to get my teeth into there! I'm reading as much as I can to understand as much as possible!!
love the cat pic too!!!

 

Welcome to AAC!

I'm a total newbie to electronics but thought I'd give it a go just for a hobbie.

You should start off by reading the datasheet and stop abusing your Nano. Nano uses the same microcontroller as the Uno, ATmega328P. The outputs weren't design to drive 40mA loads:

Devices aren't guaranteed to survive absolute maximum ratings.

Here's a note on the same page that mentions the test condition of 20mA at Vcc=5V:

 

Here is a typical... Instead of the switch shown, it would be from a Nano pin switching @ 5V. The LED power can be whatever you have as long as it is limited to ~20mA and no more than ~12VDC or so. Any time you need to supply any real power from a Nano use a switch!

 

Welcome to AAC!

You should start off by reading the datasheet and stop abusing your Nano. Nano uses the same microcontroller as the Uno, ATmega328P. The outputs weren't design to drive 40mA loads:
View attachment 248456
Devices aren't guaranteed to survive absolute maximum ratings.

Here's a note on the same page that mentions the test condition of 20mA at Vcc=5V:
View attachment 248458
View attachment 248457

Thanks Dennis I'll certainly look into that!

 

This is one way to drive an LED with a Nano:

If you use MOSFETs instead of bipolar junction transistors (BJTs), you don't need base resistors to limit base current.

For your 28V lamps, you could replace the LED, resistor, and 5V supply with the lamp and a 28V supply (incandescent lamps don't require current limiting resistors, LEDs do).

Since you're just starting, get in the habit of drawing actual schematics. The flow in schematics flows primarily left to right and top to bottom.

A lot of people who use Arduino's like to draw wiring diagrams that look like cartoons. Wiring diagrams aren't conducive to conveying circuit intent, often with just a glance.

 

This is one way to drive an LED with a Nano:
View attachment 248460
If you use MOSFETs instead of bipolar junction transistors (BJTs), you don't need base resistors to limit base current.

For your 28V lamps, you could replace the LED, resistor, and 5V supply with the lamp and a 28V supply (incandescent lamps don't require current limiting resistors, LEDs do).

Since you're just starting, get in the habit of drawing actual schematics. The flow in schematics flows primarily left to right and top to bottom.

A lot of people who use Arduino's like to draw wiring diagrams that look like cartoons. Wiring diagrams aren't conducive to conveying circuit intent, often with just a glance.

Thanks Dennis! I already feel bad for my nano for abusing thus far! I'm thinking of 2 options:

1) find lower voltage lamps, I've seen 6.3V ones, but they have a current of 0.04A so, as you said wouldnt do my little nano any good, if i understand right, so I can keep looking or;

2) replace with LEDS and resistors, however I'de have to basically take the guts out of the housing and I really liked keeping it as original as possible, maybe I've bitten off more than I can chew as a newbie! lol, but Im enjoying it and the wife is happy I'm out of the way!

 

I'de have to basically take the guts out of the housing and I really liked keeping it as original as possible

Then just use a 28V supply and use BJTs or MOSFETs to switch them to ground. If you were using the Nano to drive the ground side of the lamps, you'd need to invert the polarity of the Nano outputs.

If you want to use a lower supply voltage, you'll need to replace the lamps. You can still drive 6V lamps with the MOSFET I suggested. If you use a transistor, if you're going to drive more than 1 lamp from an output, you need to size the base resistor accordingly. If the total current switched is less than 100mA, you can use 2N3904. You need Ib = 0.1Ic to insure that the transistors saturate. If you use MOSFETs, you don't need to worry about that. The A3400 is for over 5A at room temperature:

So one MOSFET could sink current for over 100 of the incandescent lamps.

When you get above 200mA with transistors, you need to use a power transistor.

EDIT: 2N2222 will do up to an amp.

Another option is to have the Nano drive ULN2003 darlington drivers; 7 in a 16 pin DIP. They can each sink half an amp.

 

@DarrenP Get yourself a breadboard and play around with some simple led and resistor/capacitor type circuits. Maybe some 555 IC's. You will soon get the hang of it. There is a ton of info out there. But be careful there is also a lot of rubbish on the net. You can always jack up your light later when you have more experience.

 

@DarrenP

Stay away from circuits from the likes of Mr. Ahmed. He couldn't even draw a decent cartoon. Too many unnecessary wire jogs and several unnecessary wire crossings.

 

The existing lamps are likely the old #327 28 Volt lamps. Those lamps are 1.0 watt 28 Volt bulbs. They should have a T-1.75 base. You can likely find 28 Volt LED lamps with the same base. Problem is they aren't cheap. They would be an LED replacement for a #327 bulb which I think you have. You might also find a 5 volt LED lamp with the same T-1.75 bases. This spares you yanking out sockets. The 327 was a common aircraft lamp for 28 VDC aircraft power systems.

Ron

 

Here is an update for my original post, this circuit will work as long as you don't have all of the rows lit at the same time for long periods of time.

This is just a simplified block diagram...details will be provided on request.

You could use a multi-output supply or just get a 24-28 volt supply and a DC/DC module for the Nano.

Measure those ring terminals and get an appropriate sized barrier strip for easy construction.

 

Thanks Dennis! I already feel bad for my nano for abusing thus far! I'm thinking of 2 options:

No, don't feel bad. They're small cheap micro controllers. Their fate was sealed on creation. Most will die as sacrificial chips on the alter of learning. That gentile blue smoke as it passes on lights understanding in the next generation. Some lucky few will live on as successfull projects, standing on the bones of its predecessor.