tree 325 retrofit - electrical diagram/program questions

[nickcornilsen]

I've attached a PDF file of the electrical diagram for my Tree 325 project. I'll make not claim that it conforms to any kind of electrical drawing conventions, but I'm hoping it makes enough sense... I'm hoping someone doing a quick scan of the drawing might catch something I missed that may release the magic smoke...

I wouldn't worry too much about what's on pages 4 and 5... mainly just stuff to help me physically wire the thing.

A couple other questions
I'm working on writing the programs for the KFLOP.

Do I put the MPG smooth, the axis configurations, and any other stuff I need to program, into one file inside the main {...}?
Or do I leave each program stand alone, and compile/load it to the KFLOP?

Thanks,
-Nick Cornilsen

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[TomKerekes]

Hi Nick,

I do see one problem with the wiring on sheet 1. Below the Sumtak MPG there are switches switching the KFLOP JP5 pins directly to 5V. The KFlop inputs are 3.3V inputs made 5V tolerable using a 47 ohm series resistor. It probably wouldn't cause damage but it is better to limit the input voltage to less than 3.8V. Also a pull down resistor is needed. Otherwise when the switch opens the input will just "float" to any voltage and will not necessarily go low. One approach would be to use two resistors to form a voltage divider (500ohm and 1K).

Regarding the C Programs. Yes normally they are all combined into one initialization program the initializes all the axes and your system and then enters a loop servicing whatever is needed (MPG, watchdog, switch inputs, etc..) But you can start having them in several programs which makes debugging easier.

Regards

[nickcornilsen]

Thanks.
I understand why the switches would need to be changed have the voltage divider/pull down resistors.
But, the pulses from the MPG encoder thing will be 5V also, and I've got them setup with a 1K pull UP resistor, to 5V. There's no problem with that? Or does the 1K resistor keep the voltage to the terminal lower than 3.8v?

[TomKerekes]

Hi Nick,

The 1K to +5V should be ok. That is far less severe than a dead short. This would cause:

(5V - 3.3V - 0.6V) / 1K = 1.1ma

to flow into the clamping diodes which is no big deal.

Another possibility it to pull them up to the 3.3V Supply instead. Also with the switches if the switches go to 3.3V instead of 5V you wouldn't need a voltage divider (but still a single pull down resistor).

Regards

[nickcornilsen]

Hi Nick,

The 1K to +5V should be ok. That is far less severe than a dead short. This would cause:

(5V - 3.3V - 0.6V) / 1K = 1.1ma

to flow into the clamping diodes which is no big deal.

Another possibility it to pull them up to the 3.3V Supply instead. Also with the switches if the switches go to 3.3V instead of 5V you wouldn't need a voltage divider (but still a single pull down resistor).

Regards

I see... i've made the changes to the print.

I've revised the drawing. Now, I realized I made a bone-headed mistake, thinking the relay drivers produced +24V... I have changed it to make it work with the sinking nature of the FETs. I'm concerned about the spark arresting diodes. Is what I've got on page 3, zone C7, correct?
(See the one attached to this post)

[TomKerekes]

Hi Nick,

The 5V to 3V voltage divider looks good.

The revers diodes across the relays look good.

The switches connected to JP15 pins 11 - 14 don't make sense. Maybe you just didn't finish?

Regards