Need help increasing hysterisis for comparator circuit - Page 3 - Electronic Circuits Projects Diagrams Free

ericgibbs · 20th June 2009, 09:26 AM

hi 1ab,

A point thats puzzling me is the wide limits set for the comparator, the Sim shows limits of +4V and +10V.
This suggests that once the comp reads a voltage of greater than 10V, the SUN is connected to the motor
and will remain connected until SUN falls just below +4V.
I cannot see that the PV would be able to drive the motor at 4Vish.

At the <4V cut out limit, a full 24V is applied to the motor, thats a motor voltage change of 20V!.

The circuit as designed dosnt allow for the possiblity of PV[SUN] open circuit voltage of reading > 10V when the motor is switched over to the +24V.
This causes the comp to switch on/off at the lower limit of 4V.

Could you give details of the PV [solar panel] and the motor, also whats the 'system' doing, simply: whats it for.?

What limits on SUN high/low voltage do you require.

Im sure we can come up with design ideas.

Regards

1abeng · 20th June 2009, 07:42 PM

The panel is 10W and the voltage max recorded is 18V. The motor is 24VDC / 0.8A and will operate down to 4V / 30mA. The 180 Ohm simulated load resistor allowed the panel to reach 13V / 70mA before switching to SUN. This was enough power to prevent it from going below the 4V threshold when connected to the motor.

I'll have to verify the prototype PCBA with the schematic to see why you get 10V upper threshold in simulation and I observe 13V.

Can you help me get the LM393 and relay on LTSpice?

BrownOut · 20th June 2009, 08:55 PM

Quote:

Originally Posted by 1abeng

Yes, I've already accomplished this. It does require a delay off though. I think maybe C25 may be a problem as it is being charged by the 24V+ and discharges upon switching to the lower voltage SUN. I'm removing it now to see how it affects the performance.

Sorry, I misunderstood what you said before this.

There are time delay realays, but I think they're expensive. Alternatively, you can use a simple timer configured as a delay element.

ericgibbs · 21st June 2009, 01:52 PM

Quote:

Originally Posted by 1abeng

The panel is 10W and the voltage max recorded is 18V. The motor is 24VDC / 0.8A and will operate down to 4V / 30mA. The 180 Ohm simulated load resistor allowed the panel to reach 13V / 70mA before switching to SUN. This was enough power to prevent it from going below the 4V threshold when connected to the motor.

I'll have to verify the prototype PCBA with the schematic to see why you get 10V upper threshold in simulation and I observe 13V.

Can you help me get the LM393 and relay on LTSpice?

hi 1ab,

This is from the Yahoo Spice Files. [LM393]

BTW: whats the motor on the SUN project actually driving, just curious.

EDIT:Look here for relays.
http://tech.groups.yahoo.com/group/L...%20Lib/Relays/

1abeng · 23rd June 2009, 03:33 AM

Thanks Eric for the help with the components. LTSpice is a neat tool. Better if I knew how all of the details worked. I've learned a lot through this project.

With MrAl's help offline, we were able to make some minor mods to the circuit design. I had tested putting a simulated load resistor across the panel leads when not in solar mode in order to keep the voltage from jumping past the upper threshold but I had to use a PLC to make it work.

MrAl suggested using a NPN transistor with a risistor from the Q4 output that would "switch" on the simulated load resistor. My handy Radio Shack 300 kit from my youth had a C1740 NPN transistor in it that worked beautifully.

I attached the modified circuit diagram.

THANKS FOR ALL YOUR HELP!!

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20th June 2009, 09:26 AM	#31
ericgibbs	hi 1ab, A point thats puzzling me is the wide limits set for the comparator, the Sim shows limits of +4V and +10V. This suggests that once the comp reads a voltage of greater than 10V, the SUN is connected to the motor and will remain connected until SUN falls just below +4V. I cannot see that the PV would be able to drive the motor at 4Vish. At the <4V cut out limit, a full 24V is applied to the motor, thats a motor voltage change of 20V!. The circuit as designed dosnt allow for the possiblity of PV[SUN] open circuit voltage of reading > 10V when the motor is switched over to the +24V. This causes the comp to switch on/off at the lower limit of 4V. Could you give details of the PV [solar panel] and the motor, also whats the 'system' doing, simply: whats it for.? What limits on SUN high/low voltage do you require. Im sure we can come up with design ideas. Regards __________________ Eric " Good enough is Perfect " I will NOT answer PM's requesting technical help, please use the Forum PIC tutorials: Nigel's www.winpicprog.co.uk/ Bill's: www.blueroomelectronics.com/ Last edited by ericgibbs; 20th June 2009 at 09:28 AM.

20th June 2009, 07:42 PM	#32
1abeng	The panel is 10W and the voltage max recorded is 18V. The motor is 24VDC / 0.8A and will operate down to 4V / 30mA. The 180 Ohm simulated load resistor allowed the panel to reach 13V / 70mA before switching to SUN. This was enough power to prevent it from going below the 4V threshold when connected to the motor. I'll have to verify the prototype PCBA with the schematic to see why you get 10V upper threshold in simulation and I observe 13V. Can you help me get the LM393 and relay on LTSpice?

23rd June 2009, 03:33 AM	#35
1abeng	Success! Thanks Eric for the help with the components. LTSpice is a neat tool. Better if I knew how all of the details worked. I've learned a lot through this project. With MrAl's help offline, we were able to make some minor mods to the circuit design. I had tested putting a simulated load resistor across the panel leads when not in solar mode in order to keep the voltage from jumping past the upper threshold but I had to use a PLC to make it work. MrAl suggested using a NPN transistor with a risistor from the Q4 output that would "switch" on the simulated load resistor. My handy Radio Shack 300 kit from my youth had a C1740 NPN transistor in it that worked beautifully. I attached the modified circuit diagram. THANKS FOR ALL YOUR HELP!! Attached Thumbnails