Any circuit / electronic wizards help.

[rovercoupe]

Hi I have just bought a sensor to warn of low coolant in one of my vans and I have got it working but I have a issue with the trigger wire.

its a 12v circuit which has a output that goes live when no coolant is detected so the plan was to use the output 12v signal to switch a relay to sound a buzzer and led. The problem is the output has enough amps to just about light up a led and not enough to work the relay. 
 

so I need a way to either boost the output or would a lower rated 6v relay Work? 
 

any ideas?

[SpringDon]

Not a whizz but are you sure there’s not enough to trigger a relay? Could the earth on the relay be poor, try running a wire direct to -ve to test it.

Failing that a micro latching relay should do it.

[rovercoupe]

Yeah I have tried two relays and nothing, even the led is dim.

[Raja Clavata]

Can you share the spec on the sensor? 12v should be better as it requires less current for a given power. Sounds like there is either an impedance mismatch or the output needs a pull-up or pull-down resistor hanging off of it. Also, is the buzzer and led integrated - also, what voltage is the buzzer rated for? 

[rovercoupe]

Buzzer and led are separate, the buzzer is robbed off a old warning circuit for tow at electrics and it works when hooked up to a 12v supply. 
I found this on the net with the specs,

XKC Y25 T12V
PRODUCT INTRODUCTION:
 Input Voltage: DC 5-24V
 Power Consumption: 5mA
 Output Voltage (high level): InVCC
 Output Voltage (low level): 0V
 Output Current: 1-50mA
 Response Time: 500ms
 Operating Ambient Temperature: 0~100 Celsius
 Sensor Thickness (sensitivity) Range: 0-20mm
 Communication: NPN
 Humidity: 5%-100%
 Material: ABS
 Waterproof Performance: IP67
 Operating Principle: intelligent non-contact liquid level sensor is for detecting whether
there is liquid by water induction capacitor. When there is no liquid to approach the sensor, sensor will generate certain static capacitance because of the capacitor distribution; when the liquid rises slowly to approach the sensor, the liquid parasitic capacitor will coupling to this static capacitor so that the terminal capacitance of sensor will increase; the changing capacitance signal will be input to control IC and achieve signal switch, then transform the changing capacitance value into variation of certain electric signal. Using certain algorithm to detect and judge the degree of the variation; when the variation has surpassed certain threshold value, then it means the liquid level reaches sensing point.

[SpringDon]

I still think you must have a bad connection. If the output current is 50mA then a led should only take about 20mA so it shouldn’t be dim. Fix that and you may fix the relay issue.

[vmaxphil]

Try to locate a low current reed relay to feed a 12v supply to a buzzer and led separately 

[cheddletonkev]

You could just  use a Buzzer that 

requires less than 50ma 
 

then there is no need for the relay 

[Andy H]

Use an SCR (silicon controlled relay) , It only requires a small signal voltage to control a higher voltage.

[rovercoupe]

The led if from my parts box so don’t know the spec but it’s quite bright when fed 12v direct, it was for lighting up a number plate originally. 
I have had a look at a similar relays spec and it states 150ma for the coil so it looks like I will have to find one of the relays mentioned above. 

[cheddletonkev]

It’s at possible that you could have damaged the sensor output with the relay you have 

have you a voltmeter so you can check you have 12v at the sensor output

 

[Raja Clavata]

15 hours ago, rovercoupe said:

Buzzer and led are separate, the buzzer is robbed off a old warning circuit for tow at electrics and it works when hooked up to a 12v supply. 
I found this on the net with the specs,

XKC Y25 T12V
PRODUCT INTRODUCTION:
 Input Voltage: DC 5-24V
 Power Consumption: 5mA
 Output Voltage (high level): InVCC
 Output Voltage (low level): 0V
 Output Current: 1-50mA
 Response Time: 500ms
 Operating Ambient Temperature: 0~100 Celsius
 Sensor Thickness (sensitivity) Range: 0-20mm
 Communication: NPN
 Humidity: 5%-100%
 Material: ABS
 Waterproof Performance: IP67
 Operating Principle: intelligent non-contact liquid level sensor is for detecting whether
there is liquid by water induction capacitor. When there is no liquid to approach the sensor, sensor will generate certain static capacitance because of the capacitor distribution; when the liquid rises slowly to approach the sensor, the liquid parasitic capacitor will coupling to this static capacitor so that the terminal capacitance of sensor will increase; the changing capacitance signal will be input to control IC and achieve signal switch, then transform the changing capacitance value into variation of certain electric signal. Using certain algorithm to detect and judge the degree of the variation; when the variation has surpassed certain threshold value, then it means the liquid level reaches sensing point.

With NPN you switch the ground, how have you got this wired up?

[Raja Clavata]

[rovercoupe]

It is wired up so it has a positive output, don’t know how just took readings off it by testing the leads, it seems to be switchable by changing where the ground goes in. I found a cheap relay on eBay to try. 
brown is +

yellow is + output for low water

i think I wired blue for - input
 

[Demonic69]

You could use a mosfet or a transistor as a switch. I've done the same for low current outputs to boost them enough to switch a relay

[Raja Clavata]

2 hours ago, rovercoupe said:

It is wired up so it has a positive output, don’t know how just took readings off it by testing the leads, it seems to be switchable by changing where the ground goes in. I found a cheap relay on eBay to try. 
brown is +

yellow is + output for low water

i think I wired blue for - input
 

From what you've described you need to wire it as per the diagram I posted. The load being the relay coil wires, one side to the common supply and the other to yellow. Blue to chassis ground and leave the mode wire hanging (normally open configuration).

[rovercoupe]

Thanks for the drawing and explanation, I have just got it all wired up and it now activates the relay and it buzzes away happily when there is low coolant. 
now to fix the leaking pipes!

[Raja Clavata]

On 04/06/2020 at 13:27, rovercoupe said:

Thanks for the drawing and explanation, I have just got it all wired up and it now activates the relay and it buzzes away happily when there is low coolant. 
now to fix the leaking pipes!

Awesome!