Need Transistor to relay help ASAP

i'm working on a defunct Mobility scooter speed controller, the relay that powers the forward is no longer functioning. I have determined that the relay is functional.

I am trying to use a transistor to activate the heavier load relay. I found the signal from the throttle control. It rests at 5vdc and as forward throttle is increased the Vdc increase to a max of 10Vdc. For the reverse the opposite happens and the Vdc decreases to 0Vdc. The solenoid that activates the reverse engages around 4vdc.

I want the Transistor to activate at 6Vdc and above and have a through put on the High power side of 24-40Vdc. I found a NPN 2N4401 transistor from Radioshack, from what I read it should be appropriate to my task.

I'm having trouble making it work though. Did I miss my understanding of how this transistor works or how it activates? It's my first time dealing with transistors and have been reading for several days and my brains mush.

Thanks

 

from what I understand the circuit is set up so that E=24vdc B=6vdc and C= ground

The relay Transfer the power from the battery direct to the motor at 70 amps. I need the transistor to activate the relay at 6Vdc+ once throttle is applied. there is an array of relays that control the power on/off and forward and reverse. I can manually activate the relay and the trottle functions as designed, I just cant get the Circuit board to provide the activation to the relay. Hence building an external circuit to do it.

 

Ok so I have the C and E reversed. Now I'm lost again. What do I need to do to get this to activate and my 6Vdc?

the transistor I have is


Power dissipation: 350mW
Collector emitter voltage: 40V
Collector base voltage: 60V
Emitter base voltage: 6.0V
Collector current: 600mA
Case type: T0-92
Electrical Characteristics
h(fe): 100-300
f(t): 250MHz
Case type: TO-92
V(CE): 0.4
V(BE): 0.95





Or what would be the correct Transistor for my application?

 

Ok, that a clearer explanation. What am I looking for in my values? I'm sorry for the Newb questions, this is my first time dealing with a transistor, and I need a little hand holding apparently.

I read that using an inline resistor on base to reach the Saturation (on) is recommended, i'm guessing that would be easier then trying to find a transistor that is already set to that values I need.

So using the transistor I have what is my base On voltage need to be? so that I I can get the appropriate resistor? This project is quickly surpassing my knowledge level

 

let me see if I understand, or if I'm way off. I use the comparator to only pas voltage through it at my desired Base input? then use the output of the comparator to the transistor base to activate the Switch function of the transistor? I hope maybe? could I do the same thing with a resistor if it drops the 6vdc to the voltage the Base needs to activate, or will having voltage passing through the base, even if it's below the activation point damage the transistor or relay?

Sorry for all the long questions but I really have to have this running tomorrow morning

 

thanks for bearing with me, it's a lot of new info in a short time, I'm learning lots of info, and I appreciate all the help

 

OK, lets see if i understand now.......


Voltage comparator to control output of signal voltage (effectively removing all voltage below 6v from signal) then use a resistor from the output of the comparator to achieve the desired input to the transistor's base to allow sufficient voltage to activate the hi voltage/amperage relay?

I wouldn't need transistor at all except that the relay needs more then 6v to activate, correct?

I think I'm getting the picture

If i'm correct above, how do I setup the read the specs of a comparator to have it output the proper voltage, how do I read the transistor so that I can modify the output of the comparator to meet the transistors needs?

i'm drawing a diagram in paint to hopefully explain what I'm thinking

 

Thanks, it's a crash course no doubt. I'm drawing up a basic schematic to see if I have it down. I will need some help to make sure its correct and fill the values so I can hopefully get to radioshack and get the appropriate parts to get this thing back together.

 

ok here goes, What I need to figure out is what comparator to get, what resistors I need to make the the input voltage match the comparator's input specs, what resistor I need to match the transistors Base input and hopefully I solder everything up and the relay activates when Positive throttle is applied

 

doing more reading........



It looks like the comparator uses V- as a reference voltage, and V+ as the variable voltage Making my thought of needing resistors on V+ and V- not needed?


So if I have a constant Voltage +5Vdc on V-, what ever voltage beyond 5Vdc the signal wire sends will be sent through the comparator? Will the comparators output follow the increase in input voltage too? IE input is 5Vdc-10Vdc output will be 5Vdc-10Vdc as well.

If so, will this change in voltage affect my transistor base input? Do I need some sort of voltage regulator between the Comarators output and the Transistors base to hold the voltage at a constant? then use a resistor to get that voltage to the level the transistor's base needs to function?