Help with LED light, trying to have it turn on when it is plugged in. - Page 1
Forum section: electronics / projects

author: jeffie7
author_rank: Newbie
timestamp: November 16, 2020, 07:19:55 pm
content: I have a Playstation video game LED lightthat I would like to plug into a power strip that is shared with some Retro video game systems. When the power strip is flipped to on, I want the light to light up, and when it is off, I would like the light to turn off.The issue is that the light is setup so that when the tactile switch is pushed, it goes from off to on, push it again, it does a fade in/out light program, push it again and it reacts to sound, push it a 4th time and it turns off. I cannot simply leave the circuit connected or it just stays off. The connection has to be broken and then connected in order to turn the light on.Looking for recommendations on how to get the light to automatically turn on when it sees power. Ideally with the option to use the switch to change the functions, but worst case, bypassing the switch all together and having a solid on is fine.

author: james_s
author_rank: Super Contributor
timestamp: November 16, 2020, 08:39:24 pm
content: I'm betting that is a microcontroller on that board, and all of the functions are controlled by that. You won't have access to the original source code to modify that and it may by the one time programmable type anyway so your option there would be to write it all from scratch, replacing the chip with something like an AVR or whatever you are familiar with.A simpler way that may work well is just add a little circuit that effectively pushes the button once when power is applied. A relay connected across the button and controlled by a one-shot circuit would do, a transistor, resistor and capacitor can be used to create a small delay so the relay will activate once and then just sit there until power is shut off and turned on again.

author: jeffie7
author_rank: Newbie
timestamp: November 17, 2020, 01:54:56 am
content: I was thinking some type of relay but wasn't sure if it would work if it instantly kicked on. I'm pretty noobish when it comes to electronics, I've been doing a lot of video game repairs but replacing items isn't nearly as hard as coming up with things.I'm going to dig into transistors and relays, I know the basics, but would like to get deeper into understanding them.Thanks for pointing me in the right directly, that is what I had in mind but I was missing the other needed parts. =)

author: james_s
author_rank: Super Contributor
timestamp: November 17, 2020, 02:42:34 am
content: The button is probably logic level so you might be able to just connect the output side directly to the IO pin of a small microcontroller. This sort of trivial task is something that the cheap little 8 pin microcontrollers you can get are well suited to, you could slap a attiny13 in there with about 5 lines of code to wait a couple seconds, then set the pin low or high (whateve the button does) for a moment and then stop in an infinite loop doing nothing. Whether you'd like to start programming microcontrollers or do some analog design this is a nice simple project with a zillion different ways to do it and very little chance of blowing up anything expensive.

author: jeffie7
author_rank: Newbie
timestamp: November 17, 2020, 03:09:30 am
content: Random thought. Is there a slow charging capacitor I could put on the front side of the switch? Once charged it could complete the circuit and bypass the switch. Of course once it’s charged I wouldn’t be able to use the button. Not sure if a large resistor or 3 could allow for a tiny delay, long enough to allow it to turn on the light.

author: Phoenix
author_rank: Frequent Contributor
timestamp: November 17, 2020, 03:51:00 am
content: How intact do you want to keep it? Are you willing to gut the electronics and light the LEDs directly with incoming supply?

author: james_s
author_rank: Super Contributor
timestamp: November 17, 2020, 04:02:08 am
content: That's not really how capacitors work. If you put one across the switch it will delay the rate at which the voltage across it rises but it probably won't be long enough to cause the light to turn on, and it's going to affect the operation once it is on.

author: jeffie7
author_rank: Newbie
timestamp: November 17, 2020, 01:15:33 pm
content: How intact? It’s a fall back but don’t really care so my fall back would be to remove the board and figure out how much current the LEDs need and simply wire them up with a resistor.As for the capacitor not being meant for that. I was just trying to think of a way around it lol. For the sake of learning. What issues could it cause having a cap in the circuit? Once charged I would think it would stay charged until power was removed. I know capacitors can be used for filtering. Not sure if it would cause the led to flicker or act weird?I truly am a greenhorn so don’t mind the silly questions.

author: Zero999
author_rank: Super Contributor
timestamp: November 17, 2020, 01:19:35 pm
content: Quote from: jeffie7 on November 17, 2020, 01:54:56 amTry a relay, which won't be instant. It'll take a few milliseconds to turn on, which might be long enough. A timer relay is another option. Yse an off the shelf part, or make your own with an ordinary relay and a 555 timer.

author: jeffie7
author_rank: Newbie
timestamp: November 17, 2020, 01:19:39 pm
content: Adding microcontrollers to my list of things to look into. Worst case even if something did get fried I would just install my own led lights in it.This PlayStation light is meant to be used as a warning light that I’ve left my power strip on. Some of the older video game systems’ power adaptors hum and get a bit warm. I’d rather they stay unconnected to any power source since they are hardly used.

author: james_s
author_rank: Super Contributor
timestamp: November 17, 2020, 08:58:26 pm
content: I mean the really easy way to go about this all is just simply bypass the controller so that the LEDs receive power all the time. This would remove the ability to use any of the other modes though.

author: jeffie7
author_rank: Newbie
timestamp: December 15, 2020, 02:38:14 pm
content: Long over due update. I put this together a few weeks ago and tested it with the light, it seems to work fine, now it is just a matter of building it. Between work, and kids, it takes me forever to get anything done.555 timer, cap, resistor, and a relay switch.

author: james_s
author_rank: Super Contributor
timestamp: December 15, 2020, 07:12:24 pm
content: If it works then that'll do it.You might want to add a diode across the relay coil to prevent the inductive spikes it generates from damaging the IC over time. It's also advisable to use a transistor to control the relay, something like a 2N3904 would do nicely.

author: Zero999
author_rank: Super Contributor
timestamp: December 15, 2020, 08:25:27 pm
content: Yes, a back-EMF diode across the relay, is a good idea, but the NE555 can source up to 200mA: more than enough for a small relay. A 10µF capacitor across pins 1 & 8 of the 555 timer is also a good idea.

author: james_s
author_rank: Super Contributor
timestamp: December 15, 2020, 09:25:28 pm
content: I forget sometimes that the classic 555 can drive so much current. I'm used to modern cmos stuff where 20mA is pushing it.

author: Distinctly Average
author_rank: Contributor
timestamp: December 15, 2020, 11:04:05 pm
content: I saw one of these a while back with schematic on a website. Cannot find it right now. IIRC it was a micro controller, but the output drove a mosfet. You could probably just slap in a resistor to turn on the mosfet instead of letting the micro do it. You could put that resistor on a switch so you then keep all the features of the original.

author: Zero999
author_rank: Super Contributor
timestamp: December 16, 2020, 09:07:25 am
content: I also like to put a diode from the timing capacitor, to the power rail, to ensure it discharges quickly, when the power is disconnected. It means the circuit will reset quickly and the voltage on the 555 timer inputs doesn't exceed the supply voltage. A capacitor from pin 5 to 0V is also generally recommended.https://www.eevblog.com/forum/beginners/how-to-build-a-555-timer-circuit-for-5-seconds/msg1699313/#msg1699313