I’m using an LED strip with 60 LEDs for my clock. The problem I’m facing is that the moment all the LEDs are on (for a rainbow effect), the bluetooth module gets switched off. I’ve tried it with a 3.5Amp 5V power supply as well as a 1Amp 7.5V power supply. Both the module and the LED strip are connected in parallel. I’m guessing the LED strip is pulling all the power and the bluetooth module is not getting enough juice. Any suggestions please.
http://dushyant.ahuja.ws/2014/04/led-clock/
Probably just enough voltage drop to cause the BT module to reset. It takes a moment or two for a supply to adjust to a large current demand and this will probably be seen as a momentary voltage drop.
You don’t say what processor board you are using. But if it has its own on-board regulator with enough capacity, power the BT module from that to isolate it more from any voltage drops caused by the LEDs.
If this still does not work, add a good sized electrolytic or tantalum (or both) capacitor across the supply between the processor regulator and the BT module.
You could also try bringing the LEDs up slower to allow the supply to cope better or re-initialising the BT module periodically (bit of a fudge), if comms have been lost.
There are more solutions if more info available.
Thanks @Adam_Sharp - I’m using a home-made board with an atmega328 - so no on-board regulator. I’ll try to put in a capacitor across the power supply for the BT module. How would I re-initialise an HC-05 from software? The schematics and code are in the link.
Followed your link, but did not find a schematic as such. Not to worry.
Pin 11 on the HC05, instead of connecting it to +5v, attach it to an I/O pin on your 328 and then you can ‘reset’ the module at your whim. Once reset, give it a couple of seconds before talking to it after releasing the reset.
This also has the advantage that you only take the HC05 out of reset once the 328 is sane. i.e. the 328 has completed the boot loader sequence and any initialisation for your own code. And you can send it a reset whenever you want to.
Could not find on the data sheets how sensitive the onboard reset handler is, regarding power tolerances.
You may need a 10R or 100R resistor in series with the supply to the capacitor and the BT module to prevent the capacitor trying to keep the LEDs up.
A local regulator for the control logic (328 & BT, etc) is your best long term solution. This will need some voltage overhead to work. You can’t, for example, have a 5v supply, go through a 5v regulator and get 5v out. Most will need a few volts higher on the input to get the specified output. So you’ll need to read the datasheets on everything. There are some 5v to 5v DC/DC converts around that may do the job for you.
I tend to have a beefy 5v (or whatever) regulated supply for the LEDs and a smaller power supply for my logic stuff, and then this goes through high quality regulation before going to the control logic stuff. With all the GND/Ov joined together to reference everything. This stops the variations in the supply upsetting the logic stuff. Don’t put ‘dirty’, stuff on your good supplies.
Thanks @Adam_Sharp - its working with a 12V 2 Amp adapter - but goes down every 15-20 minutes. Would two 7805s work? One for LEDs and one for the logic circuits? I don’t want to connect two adapters - as this is wall mounted and the less number of wires the better.
Would a 5V 1.5 Farad capacitor help?
That is a big capacitor!
I was thinking more around the 100 to 1000uF electrolytic mark.
If your LEDs run off the12v supply, then just tap the 12v with a regulator to generate the 5v you need. Put a 1000uF on the front of the regulator and probably the same on the back. Don’t forget some 0.1uF ceramic around the regulator and maybe a 100uF tantalum on the output too. That should remove all but the largest of dips and any high frequency rubbish too. You can always make the regulator input capacitor larger if needed to protect from longer dips, but don’t forget that this will put a significant load on your 12v supply at power up too.
Are you sure its the BT module crashing the system? Not anything else? Seems odd it will run for a while before flipping out.
The LEDs also run off the 5V supply. These are WS2812B addressable RGD LEDs. Currently my 12V power supply is going through a 7805 (with capacitors and heat-sink) and powers the arduino as well as the LED strips. I’m thinking of the following three options:
- Adding the 1.5 Farad capacitor on the output of the 7805
- Reducing the brightness of the LEDs
- Two 7805s and keep one dedicated for the LEDs and one for the rest of the circuit.
This is the third version of my clock and it works fine normally - but the power supply gets over-loaded when it goes into rainbow effects. It looks amazing - so don’t really want to reduce the brightness too much.
What do you think - will the first option work - or do I have to go the whole hog and create two 5V supplies using two 7805s. Will that work?
The smoke is beginning to clear…
I suggest for your LEDs side to get a beefy 5v regulator. Not sure on the total number of LEDs you have, but looking at your photos, I think you have 4 x 60 (R,G,B with the addition of W) giving 240. Assuming 20mA per LED give a full up load of 4.8A - 240 x 0.02A.
My guess is that your current regulator for the system is going into thermal shutdown (hence the time to death). Which depending on the exact regulator could mean that it waits until it cools down and/or the load is removed. So in a worst case, you may need to turn it off until it cools down. Your capacitor won’t help here. And at 1.5F, the regulator may see it as a dead short and never power up, rr cause damage every time it is charged up at turn on. I don’t suggest adding it.
To give some overhead. I suggest you use at least a 5v regulator capable of delivering 5A or 6A. The normal 1A 7805 for your logic is fine. Make sure you read the datsheet for the big regulator and correctly size the heatsink as per the specification, or you could still be in the same position if the internals get too hot.
If this is not possible, as everything is 5v, get hold of a good 6A or 7A 5v regulated supply (this is around 35W output or better). Also as the supply you have is 12v, your 5v regulator will be struggling to dissipate the excess power too, also contributing to the heating effects apart from the raw current drain. The best voltage for 5v regulation is around 7 to 9v.
Summary: I think your current power supply is shutting down due to excess heating effects.
Does this sound more likely?
The LEDs are 3x60 - so 180 of them. The 7805 is not shutting down - I think its more a case of temporary reduction in voltage. The funny thing is that my earlier versions worked perfectly with just a single 7805. Thanks for your help - will try with the dual power supply as mentioned. Also, will replace the 12V with a 9V or 7.5 V adapter. Will post the results…
Thanks all - the plan is to now:
- setup a dual power supply - one for LEDs and one for the electronics.
- Reduce the brightness of the LEDs so that they don’t eat up my 7805.
The final result would look like:
