connection off 18v battery to transistor to arduino to 12v heating element

I have connected positive wire of 18v battery supply to the transistor(2N3904) collector. The base of the transistor have connected to the digital output pin 7 then the emitter connect to the negative wire of dc cable to 12v heating element. The positive wire of dc cable then connect back to the battery negative wire.

In the i have force to stop running for the transistor been burn.

I plan to use arduino to control the transistor when is the time to allow the supply to the heater when the condition is meet.

Addition i added the temperature sensor(lm35dt) to sense the water temperature condition.

dc cable polarity.jpg

Hi, Have you got a Digital Multimeter or a meter to measure DC Volts?

Tom.... :)

You seem to have connected the transistor as an emitter follower. That is wrong in this case.

+batt goes to the heating element, the other wire of the element goes to the collector. The batt negative goes to emitter and Arduino ground. And the Arduino output pin connects via a suitable resistor to the base.

But....

A 2N3904 is a small signal transistor. It most likely CAN'T switch that heating element.

Post details about the heating element, and the supply. Leo..

To: TomGeorge

I don have digital multimeter.

To Wawa:

The heating element is as in attachment. Originally, the element is in the heating mug that plug to the 12v cigarette lighter socket in the car to heat up the water.

i want to replace the 12v cigarette lighter by using two 9v battery connect in series.
Wat type of transistor is suitable in my task, is 2N2222 is ok?

Wawa: You seem to have connected the transistor as an emitter follower. That is wrong in this case.

+batt goes to the heating element, the other wire of the element goes to the collector. The batt negative goes to emitter and Arduino ground. And the Arduino output pin connects via a suitable resistor to the base.

But....

A 2N3904 is a small signal transistor. It most likely CAN'T switch that heating element.

Post details about the heating element, and the supply. Leo..

The heating element is as in attachment. Originally, the element is in the heating mug that plug to the 12v cigarette lighter socket in the car to heat up the water.

i want to replace the 12v cigarette lighter by using two 9v battery connect in series. Wat type of transistor is suitable in my task, is 2N2222 is ok?

IMO you should rethink your project. Either your transistor will dissipate almost as much heat as the heater element, or the heater element will burn out due to overvoltage, and also the 9V batteries will become hot and worn out pretty soon.

I'd suggest that you use a rugged 12V power supply (several Amp's) or a car or motorbike battery for the heater, and control it using a relay. The heater current (or power or resistance) must be known, before any detailed circuit and parts layout. If you don't have a heater datasheet, ask some electrical expert for measuring the values, an ordinary DVM may not be adequate and burn out during tests as well.

lancenelson: i want to replace the 12v cigarette lighter by using two 9v battery connect in series.

Let me guess. Model aircraft/ boat/ car lithium batteries?

I trust you do not mean ordinary "dry cells".

if you have a USB device, some of the coffee heater sleeves can be powered from cigarette lighter socket in car, or a USB port.

they are 5 volts and 3 watts.

using that, you have two assignments. first , size the batteries. how many minutes of life do you need ? if you need to KEEP 1 cup of coffee hot for 20 minutes, then you have one calculation

if you want to HEAT 1 cup UP TO a hot temperature, then you will need another set of calculations.

IF your heater says USB powered http://www.alibaba.com/product-detail/USB-electrical-battery-cup-warmer-sleeve_1047472361.html

then you can use a TIP-120.

not sure if you understood the location of the transistor.

your power must go directly to your heater. the transistor must be between your heater and the ground.

the heater consumes power and the transistor has less work. (transistors for dummies version) if you put your transistor to turn of the incoming power, it has to do more work. there are transistors designed to do that, but they are called P type and cost more. N type connect to ground and the 'thing' in controls. a P type goes between power and the thing it controls. both are wired up different internally.