Where is the fuse ?

[granddad]

My DIY designed green house watering controller (PIC24FV32KA302) has worked pretty good over the years , but last Friday, its LCD was blank …. seems my design was missing a vital component .. A fuse ! … the 12v pump had seized ( impeller was blocked ) when the timer fired up the IO pin the 12v battery dumped all its amps through the MOSFET and shorted the pumps winding ,as the pump is underwater it didn’t burst into flames. This destruction condition lasted till the switch died … Pump was about 150 Ohms, but finished up about one ! The drive circuit similar to this ! Lesson learned..

 

[Mike - K8LH]

Bummer!

 

[crutschow]

It's best to place the fuse at the 12V input, not the circuit output, so it protects if anything fails in the circuit also.

 

[Nigel Goodwin]

It's best to place the fuse at the 12V input, not the circuit output, so it protects if anything fails in the circuit also.

I agree, it increases protection further, at no cost.

 

[danadak]

Very simple ATTINY85 to detect pump stall, protect everything.

Code simple (this basic, not complete, starting point) .....

mBlock, takes your block code configuration, as shown above, and generates
Arduino like code to run on Arduino or an ATTINY family part.

Could even read pump heat, relative to ambient, to see if it is getting ready to fail.....

Just a thought.


Regards, Dana.

 

[granddad]

The controller is on the12v supply from a el-cheapo solar charge controller, it will limit current to 10 amps it will then shut down , unfortunately the MOSFET was only rated at 6 amps.. but my next version ( about v8 ) will have more input and output protection , and stalled motor protection .

Very simple ATTINY85 to detect pump stall, protect everything

Thanks ..I have not been entice by the Arduino maker nation, ( I am #1 PIC and 'C' fanboy ) but a current monitor is a good design feature perhaps some feedback on the high side switch may work..

 

[Nigel Goodwin]

The controller is on the12v supply from a el-cheapo solar charge controller, it will limit current to 10 amps it will then shut down , unfortunately the MOSFET was only rated at 6 amps.. but my next version ( about v8 ) will have more input and output protection , and stalled motor protection .

Pretty feeble FET

There are plenty of similar devices with vastly higher current ratings.

Thanks ..I have not been entice by the Arduino maker nation, ( I am #1 PIC and 'C' fanboy ) but a current monitor is a good design feature perhaps some feedback on the high side switch may work..

You could as easily do the exact same thing with a PIC, including an 8 pin one like the ATTINY.

However, in either case, it still make absolutely sense to have a fuse in the power rail.

I've just added a second one to the next revision of my current work project - one is on the charging input (in case the switch-mode FET goes short - or something else), the new second one is on the output of the batteries to the main circuit.

 

[granddad]

You could as easily do the exact same thing with a PIC, including an 8 pin one like the ATTINY.

Possibly but design has RTC, temperature sensor, LCD. backlight AD channel and pump drive.. oh and ICSP.. so 20 out of the PIC 28 pins

 

[Mike - K8LH]

Interesting... Does it use switches or push buttons? Schematic?

 

[danadak]

The controller is on the12v supply from a el-cheapo solar charge controller, it will limit current to 10 amps it will then shut down , unfortunately the MOSFET was only rated at 6 amps.. but my next version ( about v8 ) will have more input and output protection , and stalled motor protection .

Thanks ..I have not been entice by the Arduino maker nation, ( I am #1 PIC and 'C' fanboy ) but a current monitor is a good design feature perhaps some feedback on the high side switch may work..

If you are a C guy take a look at a single chip solution with a lot more capability for future stuff,
routable, ability to create custom onchip facilities, DSP, State Machine, and of course all the analog
onchip resources (many multiple copies) -

And community has done CPLD,. 74HC, DDS, LUTs and others for it as well added into its
fabric.

Like having a protoboard and LSI, MSI,....cabinets of parts all on one chip.

Including RTC, die T sensor....


Regards, Dana.

 

[Nigel Goodwin]

Possibly but design has RTC, temperature sensor, LCD. backlight AD channel and pump drive.. oh and ICSP.. so 20 out of the PIC 28 pins

So, if you wanted to do it, you have enough spare pins

But a fuse on the power rail should be enough anyway.

 

[granddad]

If you are a C guy

I appreciate your information , I am a very amateur C guy.. and way past my 3 score and ten , only half a dozen grey cells left ... That said your picture looks very interesting , Cheers

Interesting... Does it use switches or push buttons? Schematic?

This project is way back in my win XP and Eagle days( 2008 ). I no longer have the files well cannot find them The controller started with a sw and 3 {up /down/next buttons }, the last version used IR so I could seal the box , moisture not good for copper strip boards

 

[danadak]

I appreciate your information , I am a very amateur C guy.. and way past my 3 score and ten , only half a dozen grey cells left ... That said your picture looks very interesting , Cheers


This project is way back in my win XP and Eagle days( 2008 ). I no longer have the files well cannot find them The controller started with a sw and 3 {up /down/next buttons }, the last version used IR so I could seal the box , moisture not good for copper strip boards

I have been writing code since early 70's. Mostly now C and I am experimenting with
block languages, visual programming. I use it for simple straightforward control projects,
its faster to get up a project (no need for cheat sheet or manual by your side to insure typing
is correct), dont have to worry about variable size (for the most part), moves coder away from
strong typing type languages, like C, and is less prone to errors. Again simple stuff.

MIT, schools (6 year olds do robots), google all very active in visual languages.

I see it as the same state as C was when it was introduced. I am still waiting on a
telepathic language that just takes my thoughts and produces code. Soon I
think....

By the way the pic I showed of all the resources, they each come with a rich set
of APIs, so you largely just use API f() calls to do your coding. Many designs can be done
codeless as well just from the initial click/configure activity. Where one does not need
at runtime changes in HW....

Regards, Dana.