Brain hurts..anyone bored..

#1
just for info anyone bored and find faults?
Here i have the schematic for my project.
24v battery supplying 12v to 5v, for project and outputs for all
numerous 5v inputs, for switches
triggering 24v out, detecting and measuring a external 24v input

1557062477770.png
 
#2
….and the fault we are looking for is...?

I note that there are two PICAXEs in the drawing but only one download circuit. If both are to run at the same time, then both will need at least a pull-down resistor on their SerIn pins. Refer to "Minimum Circuit" in Manual 1.
 
#3
….and the fault we are looking for is...?

I note that there are two PICAXEs in the drawing but only one download circuit. If both are to run at the same time, then both will need at least a pull-down resistor on their SerIn pins. Refer to "Minimum Circuit" in Manual 1.
No particular fault just few people to scan over in case of sill errors
Only 1 download connection as use a dpdt switch to swap when loading
 

hippy

Technical Support
Staff member
#6
Ok great. This is the sort of info was after. Will put a 10k for each thanks
It's not necessarily that easy as you may create a potential divider. The smallest number of resistor solutions is, all resistors 22K -
Code:
                      ___
From PC >---.----.---|___|---.------> PICAXE #1
            |    |    ___    |
           .|.   `---|___|------.---> PICAXE #2
           | |               |  |
           |_|          o----'  |
            |          /        |
            |    .--- O         |
            |    |              |
        0V _|____|_     o-------'
 

Technoman

Senior Member
#8
At first sight, emitter and collector of the bipolar transistor (BC5...) are connected the wrong way round. Emitter should be connected to NEG.

At this scale, it's hard to see some details. May be a pdf file will do better.
 
#9
I don't understand the function of the FET, could you enlighten me please.
Probably obvious, but not me.
I guess he is trying to apply a reverse polarity protection with a FET. In this case, it won't work.
If I am correct, there is a fatal error since pin 3 of PicAxe20M2 receives 24V from the external 24V input.
With 24 Volts input, the regulators 7805 and 7812 will produce a lot of heat. It might be better to use a bucket-converter lika a LM2594-5 and LM2594-12. They are more energy efficiënt and produce far less heat.
Hereby I include a reverse polarity protection with a P-channel MOSFET.
 

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#10
I guess he is trying to apply a reverse polarity protection with a FET. In this case, it won't work.
If I am correct, there is a fatal error since pin 7 of PicAxe20M2 receives 24V from the external 24V input.
With 24 Volts input, the regulators 7805 and 7812 will produce a lot of heat. It might be better to use a bucket-converter lika a LM2594-5 and LM2594-12. They are more energy efficiënt and produce far less heat.
Hereby I include a reverse polarity protection with a P-channel MOSFET.
Hi, thanks for drawing :) I had drawing wrong for reverse protection. (what do people use for drawings, cant find decent and cheap with most components)
Ive not used LM2594, so clueless.. will need to look for circuit diagram... learning. for now there is very low current 24v just used for sensors (briefly one at a time)
 
#11
At first sight, emitter and collector of the bipolar transistor (BC5...) are connected the wrong way round. Emitter should be connected to NEG.

At this scale, it's hard to see some details. May be a pdf file will do better.
hi, thanks for looking
I have base with 1k input from picaxe
collector to ground
em to neg out for 24v buzzer
i with make some mods to drawing and try do pdf
 
#13
Hi, thanks for drawing :) I had drawing wrong for reverse protection. (what do people use for drawings, cant find decent and cheap with most components)
Ive not used LM2594, so clueless.. will need to look for circuit diagram... learning. for now there is very low current 24v just used for sensors (briefly one at a time)
You could use Designsparks or Kicad to draw schematics. Both programs are free and let you draw a PCB for your projects. Designsparks is promoted by RS-components where you can download footprints and schematic symbols for new components.
 

lbenson

Senior Member
#14
(what do people use for drawings, cant find decent and cheap with most components)
Eagle is free for up to (as I recall) 4" square, and most components are available if you search. Whether or not it is decent depends on how you define the word. There is a steep learning curve. The interface is less un-Windows-like than it used to be, but still some things just don't work the way you think they should.

I haven't used Designsparks, but Kicad seems widely used by hobbyists.
 

Technoman

Senior Member
#15
The symbol used for the IRL520 is a regulator's one.

As deepet noticed it, the voltage divider 1K/15K (next to 24V EXT C3 label) is not properly connected : the 1K resistor should be connected on the other side of the 15K resistor (or c3).
Doing so, the voltage on the input of the chip would be : 24 * 1/(1+15) = 1,5V which is low and would not be seen as a 1.
Taking down the 15K resistor to 4.7K would give a suitable voltage of 4,2V.

In your first post you wrote "...measuring a external 24v input " Is it this input being used for that (analog)? If so, extending the range is OK.
 
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#16
I notice that you use voltage dividers to detect the presence of 24V battery, 12V power and 24 volt external. For 24 volts this means that 1.5 volt is routed to picaxe20M2. For 12V this voltage will be around 0.75V. I think this is much to small. If you don't need to measure the voltage and only want to know if a voltage is present, I suggest to use a zener diode of 4.7 Volts wired to the 15kOhm resistor instead of the 1K resistor. The advantage is that no matter what voltage is applied (24V or 12V) the input to the 20M2 will always be around 4.7V
 
#18
The symbol used for the IRL520 is a regulator's one.

As deepet noticed it, the voltage divider 1K/15K (next to 24V EXT C3 label) is not properly connected : the 1K resistor should be connected on the other side of the 15K resistor (or c3).
Doing so, the voltage on the input of the chip would be : 24 * 1/(1+15) = 1,5V which is low and would not be seen as a 1.
Taking down the 15K resistor to 4.7K would give a suitable voltage of 4,2V.

In your first post you wrote "...measuring a external 24v input " Is it this input being used for that (analog)? If so, extending the range is OK.
thank you, i also forgot the cap for c3.
 
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