Low Voltage Motor Control Support needed

Thread Starter

corcia

Joined Jan 15, 2019
15
Hallo!
I've "assembled" a motor control circuit using few circuits found mostly on this forum; such circuit is powered by a 18650 Li battery so it has a battery charging section and a power regulation section with a 3,3V LDO voltage regulator; coming to the circuit itself it should switch on a motor (supplied with the same 3,3V of the rest of the circuit) for 2 seconds and than switch it off for 120 seconds (cyclically); while on, the current control section should switch off the motor when the current drawn by motor exceeds 60mA, the reset button will start the circuit over.
here it is:

schema si.PNG


unfortunatelly it does not work :(:(
Battery indicator, battery charger and voltage regulation are working, timer section is not, current control section seeems to work but not properly: motor stops if forced to lock down and restarts when reset is pressed but changing R7 does not change current threshold.
in the schematic above there is a missing resistor from pin 8/4 to pin 7 in real circuit such resistor is present but it doesn't work anyway.
any suggestion?

thanks!!!!!
 

Attachments

danadak

Joined Mar 10, 2018
4,057
Whats not working about timer, is it stopping ?

I noticed the Vgth of MOSFET is rated at 2 , but all the curves crap out at
4V, leaving one to wonder how turned on is that MOSFET at 3.3 ?

And the MOSFET gate is wired in schematic not to timer output but the
discharge pin, which would only turn MOSFET off, no way of turning it on.


Regards, Dana.
 

mvas

Joined Jun 19, 2017
539
Hallo!
I've "assembled" a motor control circuit using few circuits found mostly on this forum; such circuit is powered by a 18650 Li battery so it has a battery charging section and a power regulation section with a 3,3V LDO voltage regulator; coming to the circuit itself it should switch on a motor (supplied with the same 3,3V of the rest of the circuit) for 2 seconds and than switch it off for 120 seconds (cyclically); while on, the current control section should switch off the motor when the current drawn by motor exceeds 60mA, the reset button will start the circuit over.
here it is:

unfortunatelly it does not work :(:(
Battery indicator, battery charger and voltage regulation are working, timer section is not, current control section seems to work but not properly: motor stops if forced to lock down and restarts when reset is pressed but changing R7 does not change current threshold.
in the schematic above there is a missing resistor from pin 8/4 to pin 7 in real circuit such resistor is present but it doesn't work anyway.
any suggestion?

thanks!!!!!
"... switch ON a motor for 2 seconds and than switch it OFF for 120 seconds (cyclically) ..."

So, what happens at Pin #3 OUTPUT of the TLC555 ?
Does Pin #3 change state after 2 seconds and then after 120 seconds, repeat ?
What is happening to the Voltage on C2 in the Timer circuit ?
 

sghioto

Joined Dec 31, 2017
3,271
Only problem I see with the 555 circuit is that diodes D1 and D2 should be reversed if you want 2 seconds On and 120 seconds Off .
SG
 

sghioto

Joined Dec 31, 2017
3,271
any suggestion?
Modified current regulator. Control VR1 sets current level to trigger 4013. Diode added to pin2 of 4013

Modified 555 timer. FET removed. Motor controlled by connecting pin7 to collector of Q2. Timer controlled by connecting pin4 through diode to pin2 of 4013

Analysis: When power is first applied motor is off. Pin2 of 4013 is low and inhibits timer. Pressing reset switch starts motor and timer. Current overload shuts off motor and timer.
SG

EEE 4013 motor control.PNG

EEE 4013 motor control 555 timer.PNG
 

Thread Starter

corcia

Joined Jan 15, 2019
15
Modified current regulator. Control VR1 sets current level to trigger 4013. Diode added to pin2 of 4013

Modified 555 timer. FET removed. Motor controlled by connecting pin7 to collector of Q2. Timer controlled by connecting pin4 through diode to pin2 of 4013

Analysis: When power is first applied motor is off. Pin2 of 4013 is low and inhibits timer. Pressing reset switch starts motor and timer. Current overload shuts off motor and timer.
SG
View attachment 171518 View attachment 171519
Thanks a lot! this design is definetly interesting, I will give it a try, it is also prestty easy to mdify the ready made pcb to implement mods.
as per VR1 is it possible to get rid of the trimmer using a proprer resistor in R5?
 

sghioto

Joined Dec 31, 2017
3,271
as per VR1 is it possible to get rid of the trimmer using a proprer resistor in R5?
You can, after you make the current adjustment you require. Measure VR1 resistance, add 1K and replace. The only issue with this current regulator is you will lose about .75 volts through Q3. That leaves about 2.55 volts for the motor. Is that enough?
SG
 
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Thread Starter

corcia

Joined Jan 15, 2019
15
You can, after you make the current adjustment you require. Measure VR1 resistance, add 1K and replace. The only issue with this current regulator is you will lose about .75 volts through Q3. That leaves about 2.55 volts for the motor. Is that enough?
SG
is that an issue of the current regulator you posted or of the whole thing?because I'm afraid 2,55V it's not going to be a sufficient supply for the motor...
 

MaxHeadRoom

Joined Jul 18, 2013
25,183
For any motor that is RPM controlled via PWM etc, the general rule is the P.S. should be at least 10% above the motor rating.
Max.
 
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