The post details the construction of a 200 to 600 LED project, using series parallel LEDs for creating an alphabetical display sign board. The idea was requested by Mr. Mubarak Idris.
Let's Make a Blinking 200 String LED Circuit
I need a blinking LED light that show"WELCOME TO" blink and then "COLLEGE OF ENGINEERING" base on my rough estimation I'm going to use about 696 LEDs e.g for"WELCOME TO" = 216 LEDS"COLLEGE OF ENGINEERING" 480 LEDS the name welcome and college of engineering is going to flip flop and I'm thinking of connecting them to AC and only use relay to toggle the
"welcome to" and "college of engineering" alternately. hope to hear from you sir very soon and thanks in advance.
The Circuit Design
I have already discussed one related article where we learned how to calculate connect LEDs in series and parallel, in this post we are going to incorporate the same concept and formulas for estimating the connection details of the proposed 200 to 600 LED project for making the specified display sign board.
Since the LEDs are supposed to be operated from 220V mains, after rectification and filtration this would end up being at a 310V DC level.
Therefore we'll have to configure the LED groups as per the above mentioned DC level.To do this we'll first have to evaluate the total forward drop of the LED series that would fit comfortably within the 310 V limit.
Let's assume the LEDs are rated at 20mA / 3.3V, if we divide the 3.3v value with 310V, we get:
310/3.3 = 93nos.
It implies that 93 LEDs can be connected in series with the 310 input comfortably for getting an optimal illumination, however considering a possible low voltage situation and to ensure that the LEDs continue to glow even at low voltages we can go for 50% less LEDs in series, that is may be around 46 LEDs.
As per the request the welcome sign needs to have 216 LEDs, dividing this 216 with 46 gives us approximately 5 strings, in which 4 strings having around 46 LEDs in series, while the 5th could have 32 LEDs.
Therefore now we have 4 strings of 46 series LEDs and 1 string having 32 LEDs, all these strings now needs to be connected in parallel.
But as we know, in order to allow proper current distribution across the strings and allow uniform illumination, these LED strings need to have calculated resistors in series with them.
Calculating LED Current Limiter Resistor
This can be calculated with the help of the following formula:
R = Supply - Total LED FWD voltage / LED Current
= 310 - (46 x 3.3) / 0.02
here 310 is the DC supply voltage after rectification of the 220V AC supply, 46 is the total number of LEDs, 3.3 is the forward operating voltage of each LED, 0.02 is the current in amps for each LED (20mA), and 4 is number of strings.
Solving the above gives us: 7910 ohms or 7.9K, or simply a standard will 8k2 resistor will do.
wattage will be = 310 - (46 x 3.3) x 0.02 = 3.164 watts or simply a standard 5 watts resistor will do the job
the above 8k2 5 watt resistor will need to be connected with each of the strings having 46 LEDs
Now for the single 32 LEDs, we may have to follow the above procedures separately, as shown below:
R = 310 - (32 x 3.3) / 0.02 = 10220 ohms or 10.2 k or simply a standard 10K will do the job
wattage will be 310 - (32 x 3.3) x 0.02 = 4.088 or again a 5 watts will do.
Circuit Schematic
Through the above formulas we calculated the series parallel connections with resistor for configuring a 216 LED display, however, the above strings will now need to be arranged appropriately in the shape of the alphabets, corresponding to the word "WELCOME". This might require some effort and could be a little time consuming, and might require some patience and skill.
For the second group of LEDs consisting of 696 LEDs, the process will be quite similar. We first divide the 696 with 46 which gives us around 15.13, meaning 14 strings can be configured with a series of 46 LeDs and one string having 52 LEDs...all these strings will likewise need to be connected in parallel and physically arranged to represent the phrase " COLLEGE OF ENGINEERING".
The resistor values for the 46 LED strings can be as calculated in the above sections, while for the 52 LED, it may done as given below:
R = 310 - (52 x 3.3) / 0.02 = 6920 ohms or simply a 6k9 standard resistor may be used.
wattage will be = R = 310 - (52 x 3.3) x 0.02 = 2.76 watts or 3 watts
The above explanation provides us the information regarding how to build any 200 to 400 LED based project for boards or display sign boards using mains voltage without the need of a transformer.
Now, to enable the two sets of LED groups flash alternately using a relay, the following simple IC 555 flasher could be used:
The LED Flasher Circuit
R1, R2, and C can be suitably adjusted for getting the desired blinking rate over the connected 200 to 400 LED strings. The relay does not need to be a 15amp as indicated in the diagram it could be any ordinary 12v 400 ohm 5 amp type of relay
Okey Onah says
Hi swagatam. I’m Okey Onah, I really appreciate your efforts to carry us along. Please, i have a project at hand with a rectangular soft board of about 6×2 feet to design a ” WELCOME TO ENERGY CENTER ” display with a total of 620 5mm LEDs which will be mounted at the entrance of the Organization. Through your calculations here, I can design the display board with series and parallels connection, but my major challenge is to design the power supply which will feed the display perfectly without a transformer because the project is too large for transformer to power. Pls help me with a circuit of transformerless power supply suitable for this project. Thank you so kindly in advance, I am waiting to hearing from you soon.
Swag says
Hi Okey,
the above explained does not require any power supply for the LED strings. The power is taken directly from the 220V mains and then rectified using a bridge rectifier to get the required 310V DC for the LEDs.
Only the IC 555 circuit would required a 12V DC, which could be acquired from a small 12V, 500mA SMPS or from a transformer based power supply
naveen says
Dear Sir,
I would like to design one led symbol with 200 led with flashing effect .. can you please guide me the best circuit for my requirement ..
thank you sir.
Swag says
Dear Naveen, I’ll draw the design soon, and let you know…
Nishant says
Sir,
I have a 12v 40A smps supply.what can i do with it at the output (so as to not open the box) to get 5v 40A i.e same current rating.
Plz rply asap.
Swag says
Nishant, you can try the following concept
https://homemade-circuits.com/2015/03/100-amp-variable-voltage-power-supply.html
mykb says
alright thank u sir
mykb says
sir, pls kindly give me the complete circuit diagram of a PC based scrolling message display and how to program it. tnx sir
Swagatam says
mykb, presently i do not have this circuit, if possible i’ll try to find one and post it for you!
wireless says
thank u sir, am very grateful. pls another question is that, what can i use to replace LM338 regulator. i saw one of ur post dat u use LM338, i think it can handle upto 50AH battery but dat regulator is so scarce in my area, pls what can i use to replace it in dat same circuit.
Swagatam says
Wireless, you can totally avoid the LM338 stage and feed the source supply directly with the opamp stage if you can use a source current that does not exceed the specified rate, or alternatively you can add the following BJT based current controller in the middle:
https://homemade-circuits.com/2011/12/make-hundred-watt-led-floodlight.html
wireless says
gud evening sir, pls i want u to help me wit d circuit diagram of an automatic battery charger using relay, dat can handle 2 or more 12v 7.5AH connected in parallel. pls help me sir.
Swagatam says
hello wireless, you can try the first design from the following link, and adjust it for cutting off at 14V
https://homemade-circuits.com/2012/07/make-6v-4ah-automatic-battery-charger.html
mykb says
thanx for the circuit sir, but in dat circuit the last letter E that connected wit d Anode of SCR, the Cathode is not connected to anything.
Swagatam says
It seems the connection is slightly wiped off, but it is supposed to be connected with the ground line, all the cathodes are connected with the ground line.
mykb says
gud day sir, pls kindly give me the circuit diagram of LED that will be display W E L C O M E alphabet by alphabet and also blink all the letters at once 3times. tnx
Swagatam says
Hi mykb, you can try the following design
https://homemade-circuits.com/2016/09/welcome-chasing-led-display-circuit.html
wireless says
pls can u help me with circuit diagram of 16 LED and above that will be display in a sequencial form. i.e one by one
Swagatam says
just type “18 LED” in the search box, you will get the required circuit
Shahnawaz Ansari says
Hello sr please suggest me a circuit ti lit up 10000(ten thousands) led
Swagatam says
you can try the following concept
https://homemade-circuits.com/2014/04/simplest-100-watt-led-bulb-circuit.html
just go on attaching as many parallel strings as required, make sure to put a small resistor with each string
waseem riaz says
hi sir i am an aerospace engineer who truley loves your commitment and passion towards exceptional work in helping others.
sir i would appreciate if u can guide me in selecting a surge protected led driver circuit transformerless for 100 watts – 32 volts or 50 watts – 12 volts, as i recently had a burnt led of 50 watts
thank you for your amazing work have been following you for quiet some time now
Swagatam says
It's my pleasure Waseem, I think you can try the following concept for your 50 watt LED application, please make sure to upgrade the part values accordingly:
https://homemade-circuits.com/2016/07/scr-shunt-for-protecting-capacitive-led.html
Shahnawaz Ansari says
Sr how can i make 310 v dc using transformer
Swagatam says
If you are using a 12 transformer and if you feed a 12V AC from its 12V side then you might get 220V AC from its 220V side which can be rectified to get 310VDC