M
MarkMc
- Jan 1, 1970
- 0
Hi I'm a bit of a novice, and I just tested the circuit below on a
breadboard, and I find that the RL and R2 resistors are getting
incredibly hot. They are 0.25W rated. I measured the current through
R2 to be 20mA, and voltage across R2 was 10v.
Using P = IV, I make that 0.2W, and using P = I^2R, I get 0.19W, both
in spec as far as I can see. I wonder if I'm doing something else
wrong.
RL will eventually be a relay, but on the breadboard, I've made this
470R and an LED.
+-------+----+--------------
| | | +12v
.-. .-.10k|
| | | | |
RL| | | | |
'-' ___ '-' |<
+-|___|-+ -| Q2
6.8k | 10k |\
___ |/ |
On/Off Sig o-|___|-+ -| Q1 |
.-. |> .-.
| | | | |R2
10k| | | | |
'-' | '-'
| | |
| | |
=== === LED V ->
GND GND -
|
|
===
GND
Q1 = BC107B (NPN)
Q2 = BC177B (PNP)
RL = 470R
R2 = 470R
RL and R2=470 both 0.25W both get very hot
(created by AACircuit v1.28.5 beta 02/06/05 www.tech-chat.de)
Regards,
Mark
breadboard, and I find that the RL and R2 resistors are getting
incredibly hot. They are 0.25W rated. I measured the current through
R2 to be 20mA, and voltage across R2 was 10v.
Using P = IV, I make that 0.2W, and using P = I^2R, I get 0.19W, both
in spec as far as I can see. I wonder if I'm doing something else
wrong.
RL will eventually be a relay, but on the breadboard, I've made this
470R and an LED.
+-------+----+--------------
| | | +12v
.-. .-.10k|
| | | | |
RL| | | | |
'-' ___ '-' |<
+-|___|-+ -| Q2
6.8k | 10k |\
___ |/ |
On/Off Sig o-|___|-+ -| Q1 |
.-. |> .-.
| | | | |R2
10k| | | | |
'-' | '-'
| | |
| | |
=== === LED V ->
GND GND -
|
|
===
GND
Q1 = BC107B (NPN)
Q2 = BC177B (PNP)
RL = 470R
R2 = 470R
RL and R2=470 both 0.25W both get very hot
(created by AACircuit v1.28.5 beta 02/06/05 www.tech-chat.de)
Regards,
Mark