Latch On until load current continues

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Hello guys...I am wondering how to do this without burning a lot of brain cells. If there is an simple standard circuit I could use, it would be handy.

Basically I need the following:

- Atmega pin turns on a mosfet controlled load.

- Load is a motor that carries on doing something and eventually turns of by itself, so the current will drop.

- Atmega may or may not need to hold the IO pin to drive the motor.

- So some sort of latch circuit could do the tick. But the latch must turn off once the motor drops the current.

- It would be good to have some overcurrent measurement capability as well.

 

 

Last Edited: Mon. Mar 23, 2020 - 09:56 AM
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Use an SCR or thyristor instead ?

 

 

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Needs to be DC circuit...DC motor control.

To make it complicated I need to make it run in reverse direction as well.

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That's why I said SCR or Thyristor - not Triac.

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Ok I will look into SCR/Thyristor option.

I thought this could be neat circuit: https://www.edn.com/latching-pow...

Just need to remove C1 and R2.

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That does not do what you stated in the OP: it's a "push for on; push again for off" - it's not a "hold until the load stops".

 

So is that what you want?

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luvocean1 wrote:

- It would be good to have some overcurrent measurement capability as well.

 

 

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awneil wrote:

That does not do what you stated in the OP: it's a "push for on; push again for off" - it's not a "hold until the load stops".

 

So is that what you want?

which is why i said we need to remove C1 and R2 (to get rid of push to off 2nd time). 

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That will stop it latching at all - it won't make it sensitive to the load!

 

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- It would be good to have some overcurrent measurement capability as well.

Use the ADC to monitor current...If you can control the pins to turn on the motor, why do you need a "latch circuit"---just keep the pins high.  Obviously if a motor is running, plenty of power is avail, so its not like the AVR is becoming unpowered. 

 

You have an AVR at your disposal--use it!

When in the dark remember-the future looks brighter than ever.   I look forward to being able to predict the future!

Last Edited: Mon. Mar 23, 2020 - 04:32 PM