hi hgmjr,
i am back and ready when you are to finish my circuit

 

hi hgmjr,
i am back and ready when you are to finish my circuit

Where did we leave off?

hgmjr

 

we placed a 1k resistor from output of sensor to positive giving the swing of 12 volts

 

i have place in the 10k resistor from senor to base.
i am getting 0.74 volts on the base of the transistor and 1.12 volts out off the collector before the 100 ohms resistor.

 

I was thinking that we had changed the 100 ohm resistor between the HE sensor's output and the base of the first transistor to 10K. Is it still 100. That low value may be stressing your HE sensor.

hgmjr

 

i have in place the 10 k resistor

 

We also put a 1K resistor pullup on the output of the HE sensor, right?

hgmjr

 

yes we place a 1k in the circuit

 

Can you easily resketch the circuit as it is now connected and scan and post it so that we can make sure we are both on the same page?

hgmjr

 

this is it

 

That looks like what I had envisioned.

What are you seeing at the collector of the first transistor when you have a magnet near and when you don't.

hgmjr

 

You do need to lose the 1N4001 diodes in the emitters of both of the transistors.

hgmjr

 

on the collector of the first transistor i get 1.37 with out a magnet and 2.24 with a magnet over the sensor

 

sorry that was the first picture. i do not have the diodes connected

 

on the collector of the first transistor i get 1.37 with out a magnet and 2.24 with a magnet over the sensor

That sounds like the first transistor is not turning on completely.

How is the circuit working over all.

hgmjr

 

the power transistor saturates when i connect up the power supply

 

Do you have another power transistor to try in place of the one you have presently?

hgmjr

 

luck, i had to order 50 power transistor to get the order, so i have one or two spare. i get the same results.
on the collector of the power transistor i get 0.27 volts with out a magnet and 0.50 volts on the magnet

 

luck, i had to order 50 power transistor to get the order, so i have one or two spare. i get the same results.
on the collector of the power transistor i get 0.27 volts with out a magnet and 0.50 volts on the magnet

Something is not right about that behaviour.

hgmjr

 

An experiment to try would be to ground the collector of the first transistor and see if the power transistor turns off.

hgmjr