Solar Battery Protector Prevents excessive Discharge

This circuit prevents the battery in a solar lighting system from being excessively discharged. Its for small systems with less than 100W of lighting, such as several fluorescent lights, although with a higher rated Mosfet at the output, it could switch larger loads. The circuit has two comparators based on an LM393 dual op amp. One monitors the ambient light so that lamps cannot be turned on during the day. The second monitors the battery voltage, to prevent it from being excessively discharged. IC1b monitors the ambient light by virtue of the light dependent resistor connected to its non-inverting input. When exposed to light, the resistance of the LDR is low and so the output at pin 7 is low.

Circuit diagram:

Solar Battery Protector Circuit Diagram

IC1a monitors the battery voltage via a voltage divider connected to its non-inverting input. Its inverting input is connected to a reference voltage provided by ZD1. Trimpot VR1 is set so that when the battery is charged, the output at pin 1 is high and so Mosfet Q1 turns on to operate the lights. The two comparator outputs are connected together in OR gate fashion, which is permissible because they are open-collector outputs. Therefore, if either comparator output is low (ie, the internal output transistor is on) then the Mosfet (Q1) is prevented from turning on. In practice, VR1 would be set to turn off the Mosfet if the battery voltage falls below 12V. The suggested LDR is a NORP12, a weather resistant type available from Farnell Electronic Components Pty Ltd.

Author: Michael Moore - Copyright: Silicon Chip Electronics

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Inverter Overload Protector

An overload situation in an inverter may  permanently  damage  the  energy transistor array or burn off the transformer. Some of the home inverters bought in the market don't function an overload shutdown facility, whereas those incorporating this selection come with a ticket.the circuit presented here is an overload detector which shuts down the inverter  in  an  overload  situation.  

Circuit diagram:

Inverter Overload Protector With Delayed Auto Rest Circuit Diagram

 

It  hasthe following fascinating features:

• It shuts down the inverter and additionally provides  audio-visual  indication  of  the overload condition.
• after  shutdown,  it  robotically restarts  the  inverter  with  a  delay  of  6 2ds. accordingly, it keeps the consumer from the inconvenience  caused  due  to  manually resetting the device or operating round in darkness to reset the gadget at night.
• It  permanently  shuts  down  the inverter  and  proceeds  to  give  audio warning,  in  case  there  are  more  than three  successive  overloads.  Under  this situation, the device has to be manually reset.(Successive overload situation point outs that the inverter  output  is  short-circuited or a heavy current is being drawn by using the connected load.)

Inverter Overload Protector With Delayed Auto Rest

The circuit uses an ammeter  (0-30a)  as  a  transducer  to  detect  overload situation.  Such  an  am-meter  is  generally  present in  almost  all  inverters.  this  ammeter  is attached between the bad provide of the battery and the inverter, as shown in Fig. 2. the voltage developed throughout this ammeter, due to the glide of current, could be very small. It is amplified by means of IC2, which is wired as a differential amplifier having a gain  of 100. IC3 (NE555) is linked as a Schmitt ‘trigger’, whose output goes low when the voltage at its pin 2 exceeds 3.3V. IC4 (again an NE555 timer) is configured as  a  monostable  multivibrator  with  a pulsewidth of 6 seconds. IC5 (CD4017) is a CMOS counter which depends the three overload  stipulations,  after  which  the  sys-tem has to be reset manually, through urgent push-to-on change S1. the  circuit  can  be  powered  from  the inverter battery. In standby situation, it devours 8-10 ma of present and round 70 mA with relay (RL1), buzzer (PZ1), and LED1 energised. 

Please note the following factors carefully:

• Points A and B on the enter of IC2 should be connected to the corresponding points (A and B respectively) throughout the ammeter.
• Points C and D on the relay terminals  have  to  be  related  in  series  with the  already  existing  ‘on’/‘off’  switch  leads of inverter as proven in Fig. 1. which method that some of the two leads terminated on the present  swap  has  to  be  minimize  and  the  cut ends must be connected to the pole and N/O contacts respectively of relay RL1.
• The  ammeter  must  be  related in sequence with the bad terminal of the battery and inverter, as shown in Fig. 2.Move the wiper of preset VR1 to the extreme position which is grounded. Switch ‘on’ the inverter. For a three00W inverter, connect about 250-260W of load. Now alter VR1 slowly, unless the inverter simply go again and forths or shuts down.  repeat the step if vital. Use good-quality preset with dust cover (e.g. multiturn trimpot) for reliable operation.the circuit can also be simply and success-fully installed with minimum changes to the existing inverter. the entire parts used are low-cost and easily avail-able. the entire circuit is often assembled on a general-purpose PCB. The value of the entire circuit including relay, buzzer, and PCB does not exceed Rs one hundred.

Author : Siddharth Singh - Copyright : EFY Mag

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Simple DC Over voltage Protector Circuit Diagram

A very simple DC over voltage protector circuit is shown below. The transistor is set to monitor the input voltage applied to it from the left, in case the voltage rises above a specified limit, the transistor conducts, providing the required current to the SCR, which instantly fires, shorting the output and thus protecting the load from the hazard. Its also called a Crowbar circuit.
The circuit shown below is very simple to understand and is quite self explanatory.
The working may be understood with the following points:
The supply DC input voltage is applied from the right hand side o the circuit across the SCR.
As long as the input voltage remains under a certain predetermined value, the transistor is unable to conduct and therefore the SCr also remains shut.
The threshold voltage is effectively set by zener diode voltage.
As long as the input voltage stays below this threshold everything goes on fine.
However in case the input crosses the above threshold level, the zener diode starts conducting so that the base of the transistor starts getting biased.
At some point of time the transistor becomes fully biased and pulls the positive voltage to its collector terminal.
The voltage at the collector instantly passes through the gate of the SCR.
The SCR immediately conducts and shorts the input to ground.
This may look a bit dangerous because the situation indicates that the SCR might get damaged as it shorts the voltage directly through it.
But the SCR remains absolutely safe because the moment the input voltage drops below the set threshold the transistor stops conducting and inhibits the SCR from going into damaging extents.
The situation is sustained and keeps the voltage from reaching above the threshold.

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