2 direction 12VDC motor using 2 way relay boards

[rfeyer]

Les,
the only reason is that I, as an electronics novice, was afraid to please it at the input level - thinking it could possibly damage the uC, especially since adding it to the original desing caused problems (surely by erronious soldering).
Also, my apology - I thought I had answered the question of PB override placement - it is definately still placed on C/E, not B of the transistors (still have it set up)

As far as placing it at the input: Would I not need a voltage rather than just a closure of input circuit, or is the JD-VCC/ VCC combo already taking care of the voltage to trigger the relay?
Rainer

Hi Rainer,
What is the reason for putting the manual push buttons on the output of the relay board rather than the input ? Although you would need to add two diodes (Say 1N4148 and these only cost £0.0135 + VAT each) that would be much less than the saving in cost by using a cheap low current push to make push button instead of a 10 amp changeover push button.

Les.

 

[Les Jones]

To add the push buttons at the input you would connect the push button between + 5 volts and the input of the relay board. You would connect the output of the microcontroller to the input of the relay board via a diode. The positive of the diode to the relay board and the negative of the diode to the microcontroller.

Les.

 

[rfeyer]

I have the diodes, so I will give this a try this weekend.
TY for your patience

 

[rfeyer]

Les,
If I understand correctly, you suggest:
1- PB between uC 5V output and relay board VCC
2- Diode between TTL output (signal) and ini1/ ini2 on relay.

I understand the diode, which then reduced backfeed.
I don't understand how the PB close the loop to energize the relay?
Rainer

 

[Les Jones]

No The push buttons go between +5 volts and the INPUTS OF THE RELAY BOARD. Like this.

A relay can be activated either by the 5 volts output signal from the micro controller (Via the diode) to the input of the relay board or by the push button connecting 5 volt supply to the input of the relay board. The diodes prevent the 5 volts from the push buttons trying to pull the output of the micro controller up to 5 volts when it is outputting a zero volt signal. Diodes are not required from the push buttons as they do not provide an active low signal. (They are just open circuit when not pressed.)

Les.

 

[rfeyer]

OK - that I now understand!

TY

Rainer

 

[rfeyer]

I do have a question though (as always):
why is it more desirable to put the push buttons at the input side rather than output side of the relays? I would think anything at the output side is less fragile and more optically isolated? I am not criticizing, I am only asking as I do not understand

 

[Les Jones]

I agree with you comments above. The reason I suggested putting the push buttons on the input was to avoid the need for push buttons with change over contacts AND rated at 10 amps. These are probably more difficult to obtain and more expensive than the low current push to make type you could use on the input. Yet another solution that would isolate the push buttons from the micro controller would be to connect the push buttons across the outputs of the opto isolators on the relay board. I would not advise doing this unless you first post the schematic of the relay board to make sure this would be OK to do.

Les.

 

[rfeyer]

Ha,
I now see why it is better to go the DIY relay method (as per ROn schematics): more control.
I am going to use the relay board literally only to make sure I can get it to work, but will make a new circuit board when relays arrive.
Thanks to all for putting up with me,
Rainer