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A Circuit Required to Control 2 52mm red LED cluster Array

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Grzyb

New Member
Hi All,

Sorry that my first post is a request, but my mate is having a few problems....

He has bought 2 of the LED Clusters below.....From Maplins

**broken link removed**

Here are the Specs.....

52mm Red LED Cluster See Prices Below

Kingbright
A high intensity 52mm red LED cluster housed in a waterproof plastic housing that is suitable for large in or outdoor display applications such as sign or message boards. The cluster comprises of an array of super-bright GaAlAs LEDs and has a maximum luminous intensity of 23000mcd.
Specifications (IF=200mA)
Maximum luminous intensity: 23000mcd
Viewing angle: 40°
Typical forward voltage: 9.6V (11.2V)
Peak wavelength: 660nm
Maximum reverse current: 100µA VR=18V
Power dissipation: 2.5W max.
DC forward current: 250mA max.
Reverse voltage: 5V max.
Operating temperature range: -5°C to +65°C

He wants to connect them Up so as they "flash" alternatively on the top of his son's bed......

He will be using an old AT power Supply to supply the neccessary 12v to the two packs......Or will buy a battery that can provide the necessary juice

Can NE1 suggest a circuit to be able to do the required flashing, or can one be ready bought......

Hope that someone can help....

Kind Regards

Grzyb
 

crust

Member
If in fact it only draws a maximum of 250mA at 10V or so, you wont be able to use a normal PC power supply. Those supplies are switching so you must draw a minimum load from the supply. I think the load is around 5-10A or so. But for 250mA, you should be able to find a wall pack either mail order or from radio shack. A 9/10V wall pack rated at 0.5A would probably work ok (the voltage will be slightly higher at lower loads).

Then you can use a 555 oscillator configured with a 50% duty cycle to drive a pair of power transistors to switch the current between the two units.
 

Grzyb

New Member
crust said:
If in fact it only draws a maximum of 250mA at 10V or so, you wont be able to use a normal PC power supply. Those supplies are switching so you must draw a minimum load from the supply. I think the load is around 5-10A or so. But for 250mA, you should be able to find a wall pack either mail order or from radio shack. A 9/10V wall pack rated at 0.5A would probably work ok (the voltage will be slightly higher at lower loads).

Then you can use a 555 oscillator configured with a 50% duty cycle to drive a pair of power transistors to switch the current between the two units.

Thanks for the Reply......

How would I go about designing a circuit with this 555 oscillator.....

Are there any standard designs I could follow....
 

Grzyb

New Member
Then you can use a 555 oscillator configured with a 50% duty cycle to drive a pair of power transistors to switch the current between the two units.

Is there a standard circuit for this Design anywhere??
 

crust

Member
Yes, you should be able to find an example of an astable 555 circuit easily. Here is one for example:

**broken link removed**

In that circuit, you would take the output perhaps through a 1K resistor to the base of a TIP31 or other power NPN transistor (you should attach it to some simple heatsink). The emitter of the transistor should connect to your system ground and the collector to the negative lead of one of the led arrays. The anode of the led array goes to your higher voltage (10 perhaps). That will get one of them blinking. There are a couple of ways to get the other array going. One method would be to feed the output of the oscillator to an inverter and drive another transistor/array combo (be sure to run your 555 from a logic compatible voltage). Or use a different power transisitor configuration such as a pnp with your second array. There are many ways to accomplish the same idea. Note that the duty cycle will not be exactly 50%, but it will be close enough as to go unnoticed.
 
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