Moderators: Dave Moll, Andrew Davie, Steve Anderson
Klaas Robers wrote:Did you measure the voltage of the power supply while you switched on? Did it fall back to zero? And did it stay zero? If it returned to 12 volts, I would expect that everything started up again......
Can you power the motor from something else for the time being? Can you switch a resistor of several ohms in series with the motor? Do some experiments and you will see that you get feeling of where the problem hides.
Steve Anderson wrote:Quoting the Arduino Uno datasheet...
"The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts."
From what you have been saying in the past you're using a lot of resources on the Uno which as said above could overheat the regulator - and this appears to be the case.
I suggest using something like a 7808/7809 or a LM317 to pre-regulate the input voltage into the Uno. This should keep the regulator on-board from frying. I'm somewhat surprised that the say it can handle 20V...but I presume that's if the device is doing little and in sleep/shutdown mode most of the time. A rather poor and vague datasheet in my opinion. Not written for those who may not understand the consequences of excessive thermal dissipation.
In addition a pre-regulator should get rid of that 100mV of noise which is far more than I would tolerate releasing a design into the world. Chinese junk...not the sea-going vessel type.
Steve A.
Steve Anderson wrote:I suggest using the LM317 (with a heatsink) and setting the ratios of R1 & R2 to produce around 8V into the Micro. For some reason I thought you were using the Uno. This will cut down the dissipation in the on-board regulator by a factor of around three. Instead of losing 10V (15V-5V) it's only dropping 3V (8V-5V) which at the same load current is about a third of the power.
The exact same sentence is used in the Micro datasheet too.
The heatsink should not be required to be overly large.
Steve A.
Steve Anderson wrote:The IRL540 if 'typical' should be OK but you may hit a 'worst case' example. It may be worth exploring alternatives, it all depends on what you can get. In my case I find out what the local supplier has and hope to find a device suitable.
I'll have a look through some datasheets and see if there's a better device. I can't recall the total LED current.
Before ordering the PCBs check for differences in the pin-out between the TIP and the final choice of FET.
Steve A.
See if you can source an IRF540 (with an 'F' not an 'L'). You might consider an IRFD220 which is in a 4-pin DIL package, but not until you've sorted out this overheating problem.
Tried to attach two pdfs, both got stuck part way through the upload, I'll try again later.
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