Does this need a capacitor? Solved!

Projects General Guidance
1

Answer: I found out that my jumper wires and breadboard were the issue. I'm not sure if they just don't get the best connection if they can't handle the amount of current the LED strips needed but removing them solved my problem.

Original Question: I'm using a 12 volt 5 amp power supply to run 2 LED strips, one is red and one is white. If I plug both LED strips in parallel to the power supply, they work just fine. However, I want the red strip to blink on and off rapidly (100 millisecond delay) while the white LED strip stays on. I'm using a TIP 122 transistor to blink the red LEDs from my Arduino Uno. However, I've found that when the red LED strip blinks on and off, it causes some flickering (not all the way off, just dimmer) with the white LEDs.

What is causing this flickering/dimming. The LED strips are hooked up in parallel to one another so it shouldn't be the voltage. I used my multimeter and it looks like with both LED strips on, they're drawing less than .5 of an amp from the 5 amp power source.

I'm wondering if even though I have enough amps, is there a "catch up" period when the red strip turns on (drawing more amps) but the power source hasn't caught up yet. So while I should have enough amps from the power source, at the moment the red LED strip turns on, there's not enough current yet causing a flicker effect?

If this is the case, I'm wonder if either of these solutions will work? Could I use a 1000 uf capacity (biggest one I have right now) with the white LED strip to provide amps while the power source is "catching up."

OR

Instead of having the RED leds flash on and off, I could use a PWM pin to cause them to fade off and on. This would mean the RED leds don't draw all their current at once, but slowly over time. My theory is that this would give the power supply enough time to "catch up."

I'd love any help anyone could give me. I was hoping to also power my arudino from the same 12 V power supply (so I don't have to take up a whole wall socket), but I'm worried the "flickering" could damage the Arduino.

I've included a diagram of my breadboard below.

Thank you so much for any help you can give

2

Assuming everything in your schematic is correct a large cap on the power rail may help. That is strange given the specs of your power supply and the low current draw.

What is the part number of the power supply you are using? You show that you have a common ground with the arduino in your schematic, do you actually have the arduino grounded in your circuit?

3

dustin02rsx:
Assuming everything in your schematic is correct a large cap on the power rail may help. That is strange given the specs of your power supply and the low current draw.

What is the part number of the power supply you are using? You show that you have a common ground with the arduino in your schematic, do you actually have the arduino grounded in your circuit?

The 12 volt power supply is plugged into the wall and the Arduino is being powered by it's USB port-thingy from another charger. However the ground for the 12 volt is going into the ground pin of the Arduino.

However, I don't believe it's the Arduino. I just plugged both power strips in parallel with the 12 volt power supply (without the Arduino). If I quickly pull the ground pin from the red LED strip in and out of the breadboard (turning off and on the red LEDs), the white strip does the same flickering. Could it be that my power supply can handle the amps but my breadboard power rail can take that much?

Here's a link to the power source that I bought (I just got it off amazon). Thank you so much for your help!

https://www.amazon.com/gp/product/B073QTNF9F/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

4

Not sure if it's because Fritzy (proper circuit diagrams are ALWAYS better), but: it APPEARS that you use pin 1 of a TO92 part as base signal. Normally pin 2 is the base for a TO92. That's wrong and give all kinds of weird effects.

Breadboards can't carry much current (you draw a breadboard and mention you use one), so that may be another problem: internal resistance causing the white strip to dim.

5

heropants:
The 12 volt power supply is plugged into the wall and the Arduino is being powered by it's USB port-thingy from another charger. However the ground for the 12 volt is going into the ground pin of the Arduino.

However, I don't believe it's the Arduino. I just plugged both power strips in parallel with the 12 volt power supply (without the Arduino). If I quickly pull the ground pin from the red LED strip in and out of the breadboard (turning off and on the red LEDs), the white strip does the same flickering. Could it be that my power supply can handle the amps but my breadboard power rail can take that much?

Here's a link to the power source that I bought (I just got it off amazon). Thank you so much for your help!

https://www.amazon.com/gp/product/B073QTNF9F/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1

If you have the cap already I'd give it a shot and see if it helps a 1000 uF is plenty. It sounds like it could be related to a temporary shortage of power. Maybe also make sure all your connections are secure?

wvmarle:
Not sure if it's because Fritzy (proper circuit diagrams are ALWAYS better), but: it APPEARS that you use pin 1 of a TO92 part as base signal. Normally pin 2 is the base for a TO92. That's wrong and give all kinds of weird effects.

Breadboards can't carry much current (you draw a breadboard and mention you use one), so that may be another problem: internal resistance causing the white strip to dim.

I thought the same thing about the pinout but according to the datasheet Pin one is the base.

6

wvmarle:
Not sure if it's because Fritzy (proper circuit diagrams are ALWAYS better), but: it APPEARS that you use pin 1 of a TO92 part as base signal. Normally pin 2 is the base for a TO92. That's wrong and give all kinds of weird effects.

Breadboards can't carry much current (you draw a breadboard and mention you use one), so that may be another problem: internal resistance causing the white strip to dim.

I apologize, the transistor is a tip 122 darlington. I'm thinking the issue might be with the breadboard. I was hoping to build the actual circuit with a stripboard I have but I can't see anywhere on the specs how much current the stripboard can handle. However, I do have some wire that should work so I'll try wiring up the circuit without the breadboard.

Thank you!

7

Stripboards can handle several amps without problem. If in doubt, solder a wire on top of your strips.

8

Thank you everyone for your help on this.

I tried removing the breadboard and directly plugging in both strips of LEDs to the power supply and it worked! I can turn on and off the red LED strip without having it affect the white LED strip. I think it's either my breadboard or it could be the jumper wires I was using because I found I also needed to remove those as well from the circuit. I'm not sure if their AWG wasn't low enough to handle the amps or they just weren't getting a good connection or what.

I also found out that without the breadboard, the lights draw quite a bit more current (about 600 mA between the 2 strips). Instead of using the breadboard, I'll try soldering the circuit to a stripboard. I'm hoping that and using some 20 gauge wire instead of the jumper wires will solve the issue.

Thanks Again!