| Author |
Message |
xavier3333
Joined: 05 Feb 2007
Posts: 1
|
 05 Feb 2007 9:31 Voltage drop when powering relays. |
|
|
|
|
| I have a 5v relay being switched by a transistor with a switching diode across the coil. When each relay is powered the supply voltage drops by about .2 volts. Does anyone know why this is happening. I'm thinking it could be from forward voltage drop with the diode?
|
|
| Back to top |
|
 |
servicemann
Joined: 20 Jan 2006
Posts: 189
Helped: 13
|
05 Feb 2007 11:04 Voltage drop when powering relays. |
|
|
|
|
| There is some voltage on the switch transistor and there is another drop voltage on the power supply internal resistence.
|
|
| Back to top |
|
|
Sal
Joined: 29 Nov 2005
Posts: 310
Helped: 37
|
05 Feb 2007 13:20 Voltage drop when powering relays. |
|
|
|
|
Hi
It occurs because the power supply you are using either doesn't have regulated voltage or has less power than the required for your application. The solution is to use a higher amperage power supply or use a voltage regulated one.
If you think this info is useful click on "helped me" for statistics
Sal
|
|
| Back to top |
|
|
Kral
Joined: 28 Mar 2005
Posts: 1182
Helped: 187
|
05 Feb 2007 16:29 Re: Voltage drop when powering relays. |
|
|
|
|
xavier3333,
I agree with Sal. Also, the diode does not contribute to the load on the power supply while the relay is energized. The diode is reverse biased under this condition, so its current is the leakage current of the diode. The diode only conducts (momentarily) when the relay is de-energized. Under this condition, the diode current comes from the collapsing magnetic field of the relay coil, not from the supply. Its current is If[exp(-Lt/R)], where If is the relay current at the time that the circuit is opened, L = the relay inductance, R = the relay DC resistance, t = the elapsed time since the circuit was opened.
Regards,
|
|
| Back to top |
|
|
Google
AdSense
|
05 Feb 2007 16:29 Ads |
|
|
|
|
|
|
| Back to top |
|
|
umup
Joined: 04 Aug 2006
Posts: 99
Helped: 12
|
05 Feb 2007 19:56 Voltage drop when powering relays. |
|
|
|
|
What 5V regulator you use ?
And measure voltage at regulator input - maybe it drops down...
|
|
| Back to top |
|
|
fazan83
Joined: 11 May 2006
Posts: 124
Helped: 1
Location: Gurun, Kedah, Malaysia
|
02 Mar 2007 14:35 Re: Voltage drop when powering relays. |
|
|
|
|
If there is leakage between ground and power also can cause your voltage to drop. Please check your circuit ground and power whether there is a leakage between ground and power.
Also if your circuit current is not high enough to drive your input then the voltage will drop also.
|
|
| Back to top |
|
|
sonal
Joined: 10 Feb 2007
Posts: 112
Helped: 2
|
03 Mar 2007 8:15 Voltage drop when powering relays. |
|
|
|
|
| what 5v regulator u use
|
|
| Back to top |
|
|
