Hi!

Here is the project:
I bought a spotlight which contains 4x 50W LED Lamps. The spotlight is powered by a 28VDC battery. My vision is to control the spotlight with a mobile app (turn on/off and blink the LED's). Also the space inside the spotlight is limited (10cm X 7cm X 4cm at most since the existing wiring takes up much of the space) so I also have to take the size of the components in consideration. There is a flip switch on the Spotlight (I II O) which either turns on the top two LEDs, all four LEDs or turns them OFF. I am good with developing the software but horrible with electronics/ circuit design.

After creating the scheme i realized that the HC05 is not compatible with iOS so i'll probably go for a hc08 or a HM-10. Any recommendations? (I want to use both Android and iOS)

In the attachment there is my current circuit design. I want to use this DCDC Converter to get the desired 5V on the VIN Pin of the ESP. The ESP8266 controls 2 Logic-Level IRLZ34N MOSFETS which can trigger the LEDs according to the commands coming in from the Bluetooth Module. So basically it all gets controlled from the mobile app i will be developing.

As you may have noticed I am a newbie to circuit design, but is the attached scheme a feasible option? I've added all details which i think may be necessary but don't hesitate to tell me if you need some more information. Will I have to add some other components/resistors etc.? Are the components i chose fitting for those purposes?

 

How do you intend to regulate the current to the LED's?

 

The factory built spotlight was purchased - it should already have current regulation?

 

P Mosfets in diagram, but text says N Mosfets
Battery Positive connected to GROUND?
A fuse at the battery is a good idea.

HC-08 / HM-10 needs voltage?
The High-Low Switch needs an OFF position

Bluetooth and WiFi ?

 

How do you intend to regulate the current to the LED's?

I guess he doesn't ... you can get away with that ... the 50W leds I'm familiar with start emitting light at about 23V , to get full power about 33V is needed , at 28V each one is probably only drawing about 5W , still very bright , no real need for a heat-sink , and the leds will last forever ... But I'm sure there are variations between different manufacturers.

 

I guess he doesn't ... you can get away with that ... the 50W leds I'm familiar with start emitting light at about 23V , to get full power about 33V is needed , at 28V each one is probably only drawing about 5W , still very bright , no real need for a heat-sink , and the leds will last forever ... But I'm sure there are variations between different manufacturers.

"Cringe.."

Very bad practice, good way to destroy stuff.

 

Hello.

According to the datasheets, the module and the EPS8266 require a 3.3v supply.

eT

 

How do you intend to regulate the current to the LED's?

I just want to toggle the LEDs (on/off) with the mosfets.

P Mosfets in diagram, but text says N Mosfets
Battery Positive connected to GROUND?
A fuse at the battery is a good idea.
HC-08 / HM-10 needs voltage?
The High-Low Switch needs an OFF position
Bluetooth and WiFi ?

Mistakes all over the place. ^^

• i will use N Mosfets
• k ill take a fuse into consideration
• yes forgot about that one.
• didnt find the fitting switch in the schematics program to be honest
• i will only use Bluetooth

Hello.

According to the datasheets, the module and the EPS8266 require a 3.3v supply.

eT

Ok so i'll have to look for another DCDC. Or cant the onboard regulator of the esp handle the 5v?

 

The ESP8266 is an odd choice. You aren't going to use the WiFi, and so it becomes very big for the application. Consider the ATTiny85, possibly on the DigiSpark Pro Board (http://digistump.com/products/109) NOTE: You can't get it from them right now, but it is available cheap everywhere.

It's smaller, Arduino IDE compatible, and you can translate the project to an ATTiny on your own board (very small) if you want when you are done.

Take a look.

 

Perhaps one should consider the schematic,



1) The two switch contacts are shorted together. It does nothing, unless there is a a mid-position that is not shown.
2) The power source has its positive pole directly connected to GND. I am assuming the symbol is upside down and + is meant to be the top pole.
3) Assuming the terminal names are as intended for the mosfet, but it is an N-type, the body diode (in red) shorts the Source to the Drain. It will not act as a switch.
4) An N-channel mosfet in that configuration probably will not work, It should have its Source connected to GND and the Drain connected to the cathode (-) side of the device.

The presence or absence of a resistor will not make that circuit work.

 

I just want to toggle the LEDs (on/off) with the mosfets.

How do want to be able to toggle the LEDs?
With separate i/o channels (independent from each other)?

Mistakes all over the place.
Ok so i'll have to look for another DCDC. Or cant the onboard regulator of the esp handle the 5v?

Yes....mistakes everywhere...

In General, the supply level you choose will be reflected in the logic levels of the system and you want the logic levels to be consistent throughout the system if possible.
You also don’t want devices operating at their maximum voltage levels.

So, if your uC is designed to operate at 5v, then choose system components that are also designed to operate at 5v.

Key phrase here is “designed to operate at” or “recommended operating voltage”, as opposed to “Maximum voltage”.

Make sense?

eT

 

thx for the hints @ jpanhalt, yaakov and eetech.
No i just want to toggle the LEDs pairwise.

Ok so here is the updated version with none/fewer (?) mistakes.

 

Your mosfets are in the right position. The switch is still a little problematic. In position 1, it supplies power to LED's 3&4. In position 2, it supplies power to all 4 LEDs via the diode and link to position 1. In position 0, the lights will go out, but there may be a flash as you short your power supply directly to ground.

Why do you want to have a physical switch on the mosfets' supply when you are electronically switching the grounds?

Finally, unless your physical switch is make-before-break, I do not think it is a good idea to switch you logic supply like that. Have you considered having a single switch for the logic (i.e., an on/off for the whole device), then control the LEDs with that?

 

ah good point with the flash. ^^

The physical switch is basically there to conserver some power when the battery is inserted but the device is not in use. So basically I just want to power the ESP when the switch is either in Position 1 or 2. Is that what u asked?

 

ah good point with the flash. ^^

The physical switch is basically there to conserver some power when the battery is inserted but the device is not in use. So basically I just want to power the ESP when the switch is either in Position 1 or 2. Is that what u asked?

That is exactly my point. The LEDs will draw no power, when the corresponding mosfets are "off." That is, Drain-Source leakage is very low.* All you need to do is switch the logic on and off. Depending on the mosfet driver, you may need a largish resistor (10k to 100k) from each gate to ground so static can't build up and accidentally turn them on.

*EDIT: For the IRLZ34N, its breakdown voltage D-S is 55V. DS leakage current (Idss) at that voltage is 25 uA. At 28 volts and reasonable temperature, it would be considerably lower. Your on/off switch could easily switch all power to the system, not just logic. What I meant above is that when you are using the system, current leakage through the mosfets will be negligible compared to current through all the logic.

 

Oh i just noticed there is no smooth way i can lit up the LEDs just by using the switch without any control commands coming from the ESP. Or am I wrong here?
Umm... So i just have to add an Resistor in series after the Source of the mosfet?

 

Do not put anything between the source of the mosfet and ground except a wire. A resistor there may keep the mosfet from turning on. If you want a resistor to limit current through the LEDs, it can be in series between the mosfet drain and LED or LED and battery/power supply.

As for your first sentence, that is correct. The LEDs will do nothing without a command from the logic. That switch you have is unnecessary. You could use a double-pole switch to turn power to the mosfets off or on at the same time you control power to the logic.

 

Do you have any suggestion on how i could make the switch work while still being able to control the light via the app? So i have the full functionality from both the switch and the mobile app.

 

Do you have any suggestion on how i could make the switch work while still being able to control the light via the app? So i have the full functionality from both the switch and the mobile app.

I may be missing something, but you have the ESP8266 already controlling things. Wouldn’t you want use that? A single push button, for on-off, or something more complicated that allowed local dimming, on some pins seems the best approach.

As I said, I might hav missed something...

 

Yes i want to use both. So i either wanna switch on/off the LEDs (and also power the esp) using the switch. Furthermore it should be possible to control the spotlight with the app.