{"product_id":"under-voltage-lockout-relay-latching-voltage-monitor","title":"Under Voltage Lockout Relay – Latching Voltage Monitor","description":"\u003cp\u003eThis product prevents\/disconnects the load when an under-voltage condition occurs. The circuit latches the output when input sense voltage drops below the lockout threshold. Lockout threshold voltage can be adjusted using the onboard trimmer potentiometer PR1.  Tactile switch SW1 is provided to reset the latch when input sense voltage is back to normal. The circuit consists of a\u003cstrong\u003e\u003cspan\u003e \u003c\/span\u003eMAX835\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003echip, 5V Relay,\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003eBC857\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003ePNP transistor to drive the Relay, power LED, Relay\/Output LED, and tactile switch. MAX835 chip features a level-sensitive latch, eliminating the need to add hysteresis to prevent oscillations in load-disconnect applications.\u003c\/p\u003e\n\u003cp\u003e\u003cstrong\u003eMAX835\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003emicropower voltage monitors have a\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003e1.204V\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eprecision bandgap reference, comparator, and latched output in a 5-pin SOT23 package. Using the latched output prevents deep discharge of batteries and disconnects the load from the power supply when Undervoltage is detected at input sense voltage. MAX835 has a push-pull output driver. Two external resistors set the trip-threshold voltage.\u003c\/p\u003e\n\u003ch3\u003eOperation\u003c\/h3\u003e\n\u003cp\u003eConnect an adjustable power supply to CN3 and apply input sense voltage in the range\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003e3.4V to 8V\u003c\/strong\u003e, turn the PR1 trimmer potentiometer till the LED D3 is ON. Then the board is set for Undervoltage detection. For example, apply\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003e4.90V\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eto the CN3, rotate the PR1 so LED D3\/Relay is on, the circuit is set for under-voltage detection threshold of 4.90V, now increase the input sense voltage to 5V and reset the latch using SW1.\u003c\/p\u003e\n\u003cdiv class=\"simple-alert-boxes sab_info sab_normal\"\u003e\n\u003cstrong\u003eNote 1:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e Relay contacts can handle load current up to 7A, use higher contact relay for high current load. Relays up to 16A are available with the same PCB footprint (same dimensions)\u003c\/div\u003e\n\u003cdiv class=\"simple-alert-boxes sab_info sab_normal\"\u003e\n\u003cstrong\u003eNote 2:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eThe project can also be used to prevent deep discharge of batteries, it disconnects the load when battery voltage drops below the set point, read the datasheet of MAX835 to configure the input voltage range of battery using PR1 trimmer potentiometer and resistor R5.\u003c\/div\u003e\n\u003cdiv class=\"simple-alert-boxes sab_info sab_normal\"\u003e\n\u003cstrong\u003eNote 3:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003e Input sense voltage range is\u003cspan\u003e \u003c\/span\u003e\u003cstrong\u003e3.4V to 8V\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eand can be adjusted using trimmer potentiometer PR1.  The circuit can be configured to detect higher voltage. To achieve that choose the right value for PR1 and R5. Read the datasheet of MAX835 for more info.\u003c\/div\u003e\n\u003ch3\u003eConnections\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eCN1 = Pin1 VCC, Pin 2 VCC, Pin 3 GND, Pin 4 GND\u003c\/li\u003e\n\u003cli\u003eCN2= Pin 1 Sense Voltage Input, Pin 2 GND\u003c\/li\u003e\n\u003cli\u003eSW1 = Reset Switch\u003c\/li\u003e\n\u003cli\u003eD1 = Power LED\u003c\/li\u003e\n\u003cli\u003eD3 = Function LED – Relay Output\u003c\/li\u003e\n\u003cli\u003ePR1 = Trimmer Potentiometer Input Sense Voltage Adjust\u003c\/li\u003e\n\u003cli\u003eCN2 = Load Connection, Pin 1 Normally Closed, Pin 2 Common, Pin 3 Normally Open\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eFeatures\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eSupply 5V DC @ 50mA when Relay is on\u003c\/li\u003e\n\u003cli\u003eLoad Up to 7A, which can be increased -\u0026gt; Read Note 1\u003c\/li\u003e\n\u003cli\u003eInput Voltage Range 3.4V to 8V\u003c\/li\u003e\n\u003cli\u003eOn Board Tact Switch for Latch Reset SW1\u003c\/li\u003e\n\u003cli\u003eLatched Output (Once Low, Stays Low Until Cleared)\u003c\/li\u003e\n\u003cli\u003ePrecision +\/-1.25% Voltage Threshold\u003c\/li\u003e\n\u003cli\u003eLED D3, Alert Monitor – LED is ON when output is Latched (OFF)\u003c\/li\u003e\n\u003cli\u003eLED D1, Power LED\u003c\/li\u003e\n\u003cli\u003e4 x 3MM Mounting Holes\u003c\/li\u003e\n\u003cli\u003ePCB Dimensions 45.25 x 29.53mm\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"dotfry","offers":[{"title":"Default Title","offer_id":47241407660204,"sku":"B135","price":12.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0757\/6436\/7532\/files\/B135B.jpg?v=1789715877","url":"https:\/\/dotfry.com\/products\/under-voltage-lockout-relay-latching-voltage-monitor","provider":"dotfry","version":"1.0","type":"link"}