using PWM to dim LED NEON STRIP

[MrDEB]

couldn't locate this thread but here is the issue
I breadboarded this circuit and it seems to work driving just an LED but I am driving a 12v led neon strip.
The circuit flashes the strip slowly to fast as per pot adjustment.
The 555 circuit works as planned with one LED (it is supposed to change the duty cycle
Thinking the two different supply voltages has something but what to do? Any suggestions?
NOTE THE 7555 IS POWERED BY THE pic
the MOSFET is logic level

 

[MrDEB]

Am using all this info and comparing each suggestion.
Post#71 I a solar battery device. Similar to the LTC3780 but really not a bench power supply IMO

 

[MrDEB]

looking at using an ATX computer supply
researching and reviewing the RFP12N10L MOSFET DATA SHEET

 

[For The Popcorn]

Am using all this info and comparing each suggestion.
Post#71 I a solar battery device. Similar to the LTC3780 but really not a bench power supply IMO

Pardon me?

The ZK-4Kx module is a buck-boost power supply, with many features. Connect say a 12VDC power brick to it and you get:

○ 0.5 – 30 VDC constant voltage supply @ up to 35 watts.
○ Display of voltage being supplied with 0.01V resolution
○ Display of current being supplied with milli-amp resolution
○ Settable voltage limits (so you don't inadvertently crank the voltage up to 20 on your 5 volt circuit)
○ Settable current limits and short circuit protection
○ Settable power limits
○ Display of power being drawn and energy being consumed over time (amp-hours and watt-hours)

○ Constant current mode, with features as above

A manual is available here.


If you read any posts other than your own, you might see that I know something about this module. I have been using one of its cousins for years, and recently added this one to my collection.

An ATX supply is not a good option for you with your proclivity of shorting things out. The current supplied by an ATX supply is enough to vaporize components.

 

[MrDEB]

Thanks now I know what to purchase.
hesitant to buy from an unknown seller. Found Wal mart is selling one as well

 

[Nigel Goodwin]

Thanks now I know what to purchase.
hesitant to buy from an unknown seller. Found Wal mart is selling one as well

Why would you buy from Wal Mart? - so you're hesitant to buy from an 'unknown seller', but are happy to buy from a well known crap seller?. I somehow doubt Wal Mart are selling electronic modules for hobbiests in any case?.

 

[MrDEB]

Well I was able to do some limited testing of the RFP12N10L Mosfet
by limited I only had a short LED strip that draws 500ma
I have a variable power source I purchased years ago (suggested on this site) and found that the temperature of the Mosfet turns on at about 3v. The temperature started climbing. I Increased the gate voltage to 10v and temp started dropping. Found that about 5v the temp stays pretty constant but remember I am only drawing 500ma.
I need to configure a new strip and remeasure results but it looks good IMO.
Now to look on Amazon for a ZK-4KX

 

[danadak]

Why would you buy from Wal Mart? - so you're hesitant to buy from an 'unknown seller', but are happy to buy from a well known crap seller?. I somehow doubt Wal Mart are selling electronic modules for hobbiests in any case?.

Huh :

Robot or human?

Regards, Dana.

 

[For The Popcorn]

Temu has been a reliable source for me with a wide range of products. As with ALL online sellers, you need to understand the details of what you're actually buying. Temu also has free shipping that is reasonably fast.

One warning – do not install the Temu app. Order from the web page only. The app is reported to have horrendous information leaks.

 

[For The Popcorn]

I somehow doubt Wal Mart are selling electronic modules for hobbiests in any case?

Walmart's app lists all kinds of products sold by 3rd party sellers. The shipping times are long, and actually you're dealing with the 3rd party seller, not Walmart. I am pretty sure if you fall for this and something goes wrong, Walmart's not going to do anything for you.

MrDEB please understand one detail about this power supply – it CAN supply 4 amps, but its output is LIMITED TO 35 WATTS. With an appropriate power source, you can get 4 amps at 5 volts, a bit less than 3 amps at 12 volts and only about an amp at 30 volts.

 

[Nigel Goodwin]

Walmart's app lists all kinds of products sold by 3rd party sellers. The shipping times are long, and actually you're dealing with the 3rd party seller, not Walmart. I am pretty sure if you fall for this and something goes wrong, Walmart's not going to do anything for you.

MrDEB please understand one detail about this power supply – it CAN supply 4 amps, but its output is LIMITED TO 35 WATTS. With an appropriate power source, you can get 4 amps at 5 volts, a bit less than 3 amps at 12 volts and only about an amp at 30 volts.

When he said "Wal Mart is selling one", I presumed that he was walking into a Wal Mart store, and walking out with what he wanted - not just a dubious link from a Wal Mart app to an unrelated 3rd party Chinese seller. It's like Amazon, they are great - until you make the mistake of unwittingly ordering from Amazon Market place from some random dodgy Chinese company, that takes weeks to deliver.

I've no problem with using random dodgy Chinese companies, but I like to know I'm doing so.

 

[For The Popcorn]

I wish Walmart had an electronics section! Component and parts stores have all but disappeared in the US (Seattle, with a metro area population of about 3.5 million, has ONE electronics store that sells surplus, some components and some imported "Arduino" modules at an inflated price).

 

[ZipZapOuch]

I wish Walmart had an electronics section! Component and parts stores have all but disappeared in the US (Seattle, with a metro area population of about 3.5 million, has ONE electronics store that sells surplus, some components and some imported "Arduino" modules at an inflated price).

I'm so happy we no longer have Radio Shack - the last time I was in there they had 555 timers and 5-packs of red LEDs at "80% discount!" - which was still about double the price of similar parts at Digikey. I found the Digikey $6 shipping more than paid for itself in each order vs buying a few parts at the Shack

 

[MrDEB]

I ordered 2 ZK-4KX units from Amazon yesterday. Supposed to be here by the weekend

 

[MrDEB]

Diyode mag has an article almost exactly what I am building. BUT the build schematic shows 12v Vin on an Ardunio unio?
Using 100k to grd on the mosfets. The IRLZ44 MOSFETS (2 - 4v Vgs( th) instead of the RFP12N10L mosfets I plan to use.
Was/am considering using a gate driver

https://diyodemag.com/education/the_classroom_making_with_mosfets

 

[For The Popcorn]

You link does not mention gate drivers that I can see. It dies say that some mosfets won't turn fully on with a 5 volt gate signal, but fortunately logic level mosfets solve the problem.

The link does say that a microcontroller output may be limited in driving mosfets with high speed PWM. What frequency do you need to drive LEDs for dimming? Definitely does not fall into the category of "high speed".

You've read this advice before: figure out what you're trying to do, settle on a scheme and make it work. Looking for the "Holly Grail" every time you encounter the slightest bump has not done you any favors (and has driven many people who have wasted time trying to help you insane).

 

[MrDEB]

trying to learn about a proper circuit layout and components before I have another board made.
Ging from the article in diyode mag the IRLZ44 MOSFET has a much lower Rds(on) = 13.5mohms and the critical I linked to is basically the same build. The buck converters are due in tomorrow

 

[MrDEB]

If you looked at post#94 you will see the author used analog to digital code similar to Tumbleweeds suggestion in post#58 but using some really large value pots.
Another thing I see is a 100k resistor from the gate to the ground and a 240-ohm resistor from pic to the gate. The schematic shows a 10k. Misprint?
I ordered 30 of the IRLZ44's at 64 cents each plus $10 shipping. Want to test using a higher gate voltage of 10v and see how hot the buggers get. The article in post#94 doesn't mention hot much amperage or temp.

 

[tumbleweed]

If you check the datasheet for the 18F2221 you'll find the recommended source impedance for ADC inputs is 2.5K ohms. That varies with different devices. I'm not going to bother explaining why, but either use a 2.5K pot or place a small value cap, like 0.1 or 0.01uf on the ADC input pins to GND.

IMHO, use a 10K pull-down and a 100 ohm series R (or less) on the gate. The higher the value of the series R, the slower the fet will switch and that will increase the power and heat.

 

[MrDEB]

yes have made changes to schematic.
Tumbleweed suggested in post#58 5k pots and the caps. As well as the gate resistor values

 

[For The Popcorn]

Here's the operating instructions for the ZK-4KX module.