MK115 and MK100 tips please

I’m upgrading my son’s robot costume to include some LED lights.

First, I’ve used a MK115 for a voice box.
Modifications:
For longer battery life I used 2AA instead of the CR2032 watch battery.
The mic is located right in front of his mouth (inside the Robot helmet).
Used 5each 3mm LEDs on each of the 5 LED circuits (wired Parallel)(total of 25 LEDs wired in 5 groups of 5 each).

At first they were a little dim, but the guy at Altex said I could either raise the voltage, or replace the positive side resister.
It came with 10k so I bought some 5K resistors.
Since it was easier, I first tried adding an extra 1.5 volts (total 4.5 volts)
This does indeed seem brighter, but it also seems as if it is more sensitive.
I’m actually ok with it working like it does, but if I’ve done something wrong, please let me know.

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Next the MK100
This will be for flashing running lights around the Robot body.
The MK100 provides for 16 single LEDs and I want to double that to 32 total (16 pairs of 2 each wired parallel).
This one is not yet assembled so I can easily change things if that is best.
This one provides 1K2 resistors on the positive side, so I purchased some 820 ohm resistors in order to keep the brightness up.
I figure this would be OK, except now I’ve decided I want to use 5mm Blue LEDs instead of the supplied 3mm Red LEDs.

Now at first, the salesman at Altex sold me an assortment of Red, Green and Yellow LEDs (which have worked fine on the MK115).
I note the assortment box includes some specs for the LEDs as follows:
3mm green = 4.0mcd
3mm red = 1.0mcd
5mm green = 6.0mcd
5mm red = 2.0mcd
5mm yellow = 3.9mcd

5v = 330 1/4watt
9v = 680 1/4watt
12v = 1k 1/4 watt
24v = 2k2 1/4 watt

The Blue LEDs I’ve seen, compared to these numbers, are SUPER bright!!!
Ranging from 4000mcd to 15,000mcd!!!
All seem to range from 3.2 to 3.8 volts
Light angles of 25 to 40 degrees.

So now the questions:

  1. Will doubling the the LEDs on each circuit from 1 to 2 each necessitate a different resistor (a little DIM is OK)
  2. Are these Blue LEDs really that bright? Is the 4000mcd Blue LED really going to look 666 times brighter than the 6.0 Green LED?
  3. Will these Blue LEDs work? Aren’t they pretty much universal in thier specs?
  4. If the Blue LEDs really are that bright, then perhaps being a little DIM as a result of doubling them up may not be such an issue that I need to change the resistor?

Thanks for any and all help!

I’m a software developer, not an engineer, so i can’t answer your questions, i’m sure my collegues will though :slight_smile: But, i’m just curious to see a picture of that robot costume :slight_smile:

We cannot guarantee the correct operation if any of the above kits are modified, so you will have to experiment.
For blue leds, the resistor will probably have to be changed, as their drop is a lot higher than red leds.

sigh…

Believe me, I’m not looking for warranty on a $7.00 kit.
;^)

I’m lookingfor tips on how to make this effecetive so I don’t end up embarrasing my son. That is worth a lot more than $7.00.

The Blue LEDs come with resistors that I can specify in advance.
Can you suggest for me, what value I should get?

Also, does anybody know about Blue LEDs?
Are they really that bright?
Is there a better resistor value that will dim them down?

There is no such thing as ‘a resistor value for a particular colour of LED’.
That is what I meant with ‘you will have to experiment’. Basically, there is not much that can go wrong, except when the current gets to large for the transistors. If you fry a transistor, it will cost you a couple of cents to get it replaced. I’m afraid there is not much more I can explain. Furthermore, not being able to guarantee correct operation has nothing to do with warranty. I was just trying to warn you, to avoid frustration. Some circuits work fine if they are used ‘as is’. If you change the led current, attach long wires, change the voltage, etc… they might start to behave completely different. Usually it takes a lot of experience to solve such problems…