Help needed for Estes snitch with LEDs for night launch - video linked

[mjstech]

I need some electrical help with a night rocket snitch with LEDs.

Video: https://imageshack.us/clip/my-videos/836/f8a.mp4/

Parts list:

There are 12x 5mm RGB LEDs

Forward Voltage (V) : 3.5
Forward Current (mA): 20


There are 6x 3mm super white LEDs

Forward Voltage 3.5V
Current Rating 20mA
Reverse Voltage (V) 5
Continuous forward current(mA) 20
Peak forward Current(mA) 40
Power Dissipation (mW) 100


There are 2x 2032 3V batteries

CR2032 Voltage 3V
Norminal capacity 230mAh
Norminal current 0.1


Each led is run parallel to the voltage source. Batteries are run in parallel. Anode of each led is conntected to + and each cathode to -

They are wired WITHOUT RESISTORS currently.
I did buy 150Ohm restors per https://led.linear1.org/led.wiz. if I need them.

This is the info I got from that site...

Solution 0: 1 x 18 array uses 18 LEDs exactly
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms

The wizard says: In solution 0:
each 150 ohm resistor dissipates 60 mW
the wizard thinks ¼W resistors are fine for your application
together, all resistors dissipate 1080 mW
together, the diodes dissipate 1260 mW
total power dissipated by the array is 2340 mW
the array draws current of 360 mA from the source.

Problem:

I didn't use the resistors because in my test breadboard the LEDs were doing the same thing (white LEDs would dim/go off due to voltage and or current needs of the RGB leds. (You can tell when LEDs are solid red and not in 'blinking mode' the white leds dim and pretty much go off for a fraction of a second. When a lot of the LEDs are in 'blink mode' there is less voltage/current to drive them and the white LEDs are bright.

Solution Needed:

Is there anything I can do without having to add more/larger batteries to keep the white LEDs from dimming in my circuit?

Thanks, Mark

 

[mjstech]

I just hooked it up with 5 AA batteries, and there is no dimming of the white LEDs. AA batteries are rated at 400-900mAh each. So I think it is a current issue.
I don't think the coin batteries can push enough current to keep everything lit. The coin batteries push 230mAh each.
The led circuit wants at least 360mA and may be as high as 1140mA (from reading another RGB led spec for max fwd current and the max fwd currrent of the white LEDs used).
So now knowing this information I think that a capacitor may work for me.
I don't know much about them, but do remember seeing huge multi Farad ones for car stereo amps.
I have a misc bag of small capicitors in house, but don't know what I would need.

 

[UncleVanya]

A capacitor can help reduce variation in the voltage supplied to a circuit but only if it can supply the current needed to run the circuit when demand exceeds supply. In your case I don't think it will work since this isn't a short duration need - why not increase the battery current by paralleling in another two button cells? Also 5 * 1.5v = 7.5v vs 2 * 3v = 6v, so you've changed voltage as well as current which makes it hard to judge.

 

[C-57D]

I rigged up my Snitch in a similar way, except with only 3 blinking RGB LED's, the rest were UV LED's, which make the yellow plastic fluoresce pretty nicely.

I use a 12V 23A battery (about 1/2 the size of a AAA), and get the same voltage drop effect, but to me this is part of the light show... it makes the whole saucer seem to pulsate like a scene from an old "B"-grade sci-fi flick.

edit: Also, it's modified to take 24mm motors; I cut out the original MMT, replaced it with some BT-50, and used epoxy and fiberglass to secure it to the fins.

[youtube]f4hvHYCH1kY[/youtube]

 

[Montaro]

I need some electrical help with a night rocket snitch with LEDs.

Video: https://imageshack.us/clip/my-videos/836/f8a.mp4/

Parts list:

There are 12x 5mm RGB LEDs

Forward Voltage (V) : 3.5
Forward Current (mA): 20


There are 6x 3mm super white LEDs

Forward Voltage 3.5V
Current Rating 20mA
Reverse Voltage (V) 5
Continuous forward current(mA) 20
Peak forward Current(mA) 40
Power Dissipation (mW) 100


There are 2x 2032 3V batteries

CR2032 Voltage 3V
Norminal capacity 230mAh
Norminal current 0.1


Each led is run parallel to the voltage source. Batteries are run in parallel. Anode of each led is conntected to + and each cathode to -

They are wired WITHOUT RESISTORS currently.
I did buy 150Ohm restors per https://led.linear1.org/led.wiz. if I need them.

This is the info I got from that site...

Solution 0: 1 x 18 array uses 18 LEDs exactly
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms
+----|>|---/\/\/---- - R = 150 ohms

The wizard says: In solution 0:
each 150 ohm resistor dissipates 60 mW
the wizard thinks ¼W resistors are fine for your application
together, all resistors dissipate 1080 mW
together, the diodes dissipate 1260 mW
total power dissipated by the array is 2340 mW
the array draws current of 360 mA from the source.

Problem:

I didn't use the resistors because in my test breadboard the LEDs were doing the same thing (white LEDs would dim/go off due to voltage and or current needs of the RGB leds. (You can tell when LEDs are solid red and not in 'blinking mode' the white leds dim and pretty much go off for a fraction of a second. When a lot of the LEDs are in 'blink mode' there is less voltage/current to drive them and the white LEDs are bright.

Solution Needed:

Is there anything I can do without having to add more/larger batteries to keep the white LEDs from dimming in my circuit?

Thanks, Mark

Hello mark you need more current there
because you asking to the battery 390 mA but you battery capacity is 360 but every tiem the leds blink they use the peak current not the nominal current.

If i was you i will go for a 3.5V, 1Ah, 1/2AA Lithium battery (Weight 9.2g). without resistors, the 2032 is around 2 g so if you go with 3 or 4 CR2032 you sum 6 to 8 gr. plus 18 resistors weight. so i think you will have similar weight.

Regards!

 

[mjstech]

You are right that 5 AA x1.5v would have been 7.5 volts. I forgot to mention I am using junk drawer batteries and measured ~5.8 volts. Thanks for all the information so far guys.
57D, if you have 1 battery, how did you keep it stable?

 

[Micromeister]

Mark:
I used a combination of 3 and 6 volt power sources on my 2 stage snitch. all the RGB flashing and UV leds run on 6volts while the remaining red and yellow require only 3 but YOU NEED the resistors attached to each to keep them supplied properly. No capacitor needed. I'm sure if you split your Leds by voltage as well they'd work just fine.

 

[dlb]

Try using a 3.7V 1200mAh or greater 25C Lipo Battery
rechargeable, small, light and on Ebay $4.00 all day long, rechargers too at cheap prices.

https://www.ebay.com/itm/3-7V-1200m...Control_Parts_Accessories&hash=item20bca8dadc


I can power a single Flashing RGB LED about 30 to 40 hours on one 600mah 3.7 v. battery.

https://www.ebay.com/itm/10-PCS-10m...537?pt=LH_DefaultDomain_0&hash=item3346c15959

Trick to reduce power even more is don't have all the LEDS on at one time. but that requires some sort of control circuit or flashing LEDs.