2017年02月05日

###
当前版本：
jayeff , 2017年02月05日

#### 文本:

Hi, |

I do not have a cable run that long but here is the maths which may help you. This is for the power requirements only |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

In the following scenario I am assuming that the Nest Cam power cable has the same resistance rating as the Cat 5e cable. Cat 5e is 24 AWG. If the Nest cam cable uses thinner gauge wires there may be a slightly higher voltage drop due to the increased resistance but given the short distance it will only be very small |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return or ''loop'' distance, Only using 2 wires in the cable |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' According to Nest Cam specifications [https://nest.com/support/article/Nest-Cam-Outdoor-technical-specifications-and-system-requirements|here] |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Here is a power adapter '''10.5V DC 1500mA''' that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up. |

http://www.ebay.com.au/itm/1-5A-Voltage-Regulated-AC-DC-Switching-Power-Supply-4-5V-5V-6V-7-5V-9V-10-5V-12V-/251329746548?hash=item3a846b9674:g:QbYAAOSwpLNX9f1c |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel (4 battery wires are in parallel with each other and 4 earth wires are in parallel with each other), the resistance will be reduced to 1.3585 Ohms |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

The same power adapter in the link above will probably work OK when the '''6V DC''' option is selected |

Hopefully this is of some help. |

=== Update (01/14/2017) === |

Hi, |

Been reconsidering my statement that it will probably work OK on 6V with 8 wires in use. It may be that the voltage available to the camera (approx 4.6V after cable losses) will not allow it to operate at optimum level. Therefore I suggest that you use a 4 wire connection, 2 wires for battery, 2 wires for earth, and select the 7.5V option on the power supply. This will give you approx 4.8V for the camera which is closer to the 5V required. If neither of these work well use the 2 wire option at 10.5V this will give you the full 5V necessary. It will be by trial and error I think as the optimum voltage operating range of the camera is |

Been reconsidering my statement that it will probably work OK on 6V with 8 wires in use. It may be that the voltage available to the camera (approx 4.6V after cable losses) will not allow it to operate at optimum level. Therefore I suggest that you use a 4 wire connection, 2 wires for battery, 2 wires for earth, and select the 7.5V option on the power supply. This will give you approx 4.8V for the camera which is closer to the 5V required. If neither of these work well use the 2 wire option at 10.5V this will give you the full 5V necessary. It will be by trial and error I think as the optimum voltage operating range of the camera is |

"Hint" If you use the 2 or 4 wire option use only the coloured wires in the cable as that way it avoids confusion whether you have the correct wires connected at each end than if you use the whites as well. |

#### 状态:

open

2017年02月05日

###
编辑：
jayeff , 2017年02月05日

#### 文本:

Hi, |

I do not have a cable run that long but here is the maths which may help you. This is for the power requirements only |

I do not have a cable run that long but here is the maths which may help you. This is for the power requirements only |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

In the following scenario I am assuming that the Nest Cam power cable has the same resistance rating as the Cat 5e cable. Cat 5e is 24 AWG. If the Nest cam cable uses thinner gauge wires there may be a slightly higher voltage drop due to the increased resistance but given the short distance it will only be very small |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return or ''loop'' distance, Only using 2 wires in the cable |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' According to Nest Cam specifications [https://nest.com/support/article/Nest-Cam-Outdoor-technical-specifications-and-system-requirements|here] |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Here is a power adapter '''10.5V DC 1500mA''' that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up. |

http://www.ebay.com.au/itm/1-5A-Voltage-Regulated-AC-DC-Switching-Power-Supply-4-5V-5V-6V-7-5V-9V-10-5V-12V-/251329746548?hash=item3a846b9674:g:QbYAAOSwpLNX9f1c |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel (4 battery wires are in parallel with each other and 4 earth wires are in parallel with each other), the resistance will be reduced to 1.3585 Ohms |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

The same power adapter in the link above will probably work OK when the '''6V DC''' option is selected |

Hopefully this is of some help. |

=== Update (01/14/2017) === |

Hi, |

Hi, |

Been reconsidering my statement that it will probably work OK on 6V with 8 wires in use. It may be that the voltage available to the camera (approx 4.6V after cable losses) will not allow it to operate at optimum level. Therefore I suggest that you use a 4 wire connection, 2 wires for battery, 2 wires for earth, and select the 7.5V option on the power supply. This will give you approx 4.8V for the camera which is closer to the 5V required. If neither of these work well use the 2 wire option at 10.5V this will give you the full 5V necessary. It will be by trial and error I think as the optimum voltage operating range of the camera is unknown. |

"Hint" If you use the 2 or 4 wire option use only the coloured wires in the cable as that way it avoids confusion whether you have the correct wires connected at each end than if you use the whites as well. |

#### 状态:

open

2017年01月14日

###
编辑：
jayeff , 2017年01月14日

#### 文本:

Hi, |

I do not have a cable run that long but here is the maths which may help you. This is for the power requirements only (assuming that you are going to use the WiFi for video signal) |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

In the following scenario I am assuming that the Nest Cam power cable has the same resistance rating as the Cat 5e cable. Cat 5e is 24 AWG. If the Nest cam cable uses thinner gauge wires there may be a slightly higher voltage drop due to the increased resistance but given the short distance it will only be very small |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return or ''loop'' distance, Only using 2 wires in the cable |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' According to Nest Cam specifications [https://nest.com/support/article/Nest-Cam-Outdoor-technical-specifications-and-system-requirements|here] |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Here is a power adapter '''10.5V DC 1500mA''' that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up. |

http://www.ebay.com.au/itm/1-5A-Voltage-Regulated-AC-DC-Switching-Power-Supply-4-5V-5V-6V-7-5V-9V-10-5V-12V-/251329746548?hash=item3a846b9674:g:QbYAAOSwpLNX9f1c |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel (4 battery wires are in parallel with each other and 4 earth wires are in parallel with each other), the resistance will be reduced to 1.3585 Ohms |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

The same power adapter in the link above will probably work OK when the '''6V DC''' option is selected |

Hopefully this is of some help. |

=== Update (01/14/2017) === |

Hi, |

Been reconsidering my statement that it will probably work OK on 6V with 8 wires in use. It may be that the voltage available to the camera (approx 4.6V after cable losses) will not allow it to operate at optimum level. Therefore I suggest that you use a 4 wire connection, 2 wires for battery, 2 wires for earth, and select the 7.5V option on the power supply. This will give you approx 4.8V for the camera which is closer to the 5V required. If neither of these work well use the 2 wire option at 10.5V this will give you the full 5V necessary. It will be by trial and error I think as the optimum voltage operating range of the camera is unknown. |

"Hint" If you use the 2 or 4 wire option use only the coloured wires in the cable as that way it avoids confusion whether you have the correct wires connected at each end than if you use the whites as well. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

I do not have a cable run that long but here is the maths which may help you. This is for the power requirements only (assuming that you are going to use the WiFi for video signal) |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

I do not have a cable run that long but here is the maths which may help you. This is for the power requirements only (assuming that you are going to use the WiFi for video signal) |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return or ''loop'' distance, |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return or ''loop'' distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' According to Nest Cam specifications |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' According to Nest Cam specifications |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

I do not have a cable run that long but here |

I do not have a cable run that long but here |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

I do not have a cable run that long but here are the maths which may help you. This is for the power requirements only (assuming that you are going to use the WiFi for video signal) |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Here is a power adapter |

Here is a power adapter |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

The same power adapter in the link above will probably work OK when the |

The same power adapter in the link above will probably work OK when the |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

I do not have a cable run that long but here are the maths which may help you. This is for the power requirements only (assuming that you are going to use the WiFi for video signal) |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Here is a power adapter 10.5V 1500mA that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up. |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel (4 battery wires are in |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel (4 battery wires are in |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

The same power adapter in the link above will probably work OK when the 6V option is selected |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

I do not have a cable run that long but here are the maths which may help you. This is for the power requirements only (assuming that you are going to use the WiFi for video signal) |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Here is a power adapter 10.5V 1500mA that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up. |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

The same power adapter in the link above will probably work OK when the 6V option is selected |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
编辑：
jayeff , 2017年01月12日

#### 文本:

Hi, |

Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' |

http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf |

Your distance is 25' Nest Cam power cable + 70' extension. |

'''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, |

'''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' |

Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' |

Here is a power adapter 10.5V 1500mA that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up. |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel $ battery wire ar ein parallell with each other and 4 earth wires are in parallel with each other, the resistance will be reduced to 1.3585 |

If you use all 8 wires in the Cat 5e cable i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel $ battery wire ar ein parallell with each other and 4 earth wires are in parallel with each other, the resistance will be reduced to 1.3585 |

Therefore new scenario will be: |

'''Total distance = 190' '''(25+70 x 2) |

'''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' |

'''Power requirements of camera is 5V DC 1.0A (1000mA)''' |

'''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' |

Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' |

The same power adapter in the link above will probably work OK when the 6V option is selected |

Hopefully this is of some help. |

#### 状态:

open

2017年01月12日

###
原帖由：
jayeff , 2017年01月12日

#### 文本:

Hi, I do not have a cable run that long but here are the maths which may help you. This is for the power requirements only (assuming that you are going to use the WiFi for video signal) Cat 5e UTP DC resistance is '''28.6 Ohms per 1000'''' http://lib.store.yahoo.net/lib/yhst-94020529776231/A7L504.pdf Your distance is 25' Nest Cam power cable + 70' extension. In the following scenario I am assuming that the Nest Cam power cable has the same resistance rating as the Cat 5e cable. Cat 5e is 24 AWG. If the Nest cam cable uses thinner gauge wires there may be a slightly higher voltage drop due to the increased resistance but given the short distance it will only be very small '''Total distance = 190' '''(25+70 x 2) The x 2 is the return distance, '''Total resistance of wiring''' : 28.6/1000 x 190 ='''5.434 Ohms''' '''Power requirements of camera is 5V DC 1.0A (1000mA)''' '''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''5.434V''' Therefore '''Supply Voltage '''required is 5V + 5.434V = '''10.434V''' Here is a power adapter 10.5V 1500mA that should be suitable for your requirements. Ensure that the polarity is correct when you connect it up. http://www.ebay.com.au/itm/1-5A-Voltage-Regulated-AC-DC-Switching-Power-Supply-4-5V-5V-6V-7-5V-9V-10-5V-12V-/251329746548?hash=item3a846b9674:g:QbYAAOSwpLNX9f1c If you use all 8 wires i.e. 4 for the battery +ve and 4 for the ground(Earth ) because they are all in parallel $ battery wire ar ein parallell with each other and 4 earth wires are in parallel with each other, the resistance will be reduced to 1.3585 Therefore new scenario will be: '''Total distance = 190' '''(25+70 x 2) '''Total resistance of wiring''' : 28.6/1000 x 190/4 ='''1.3585 Ohms''' '''Power requirements of camera is 5V DC 1.0A (1000mA)''' '''Voltage drop over cable''' at '''1.0A (1000mA) '''(Ohms Law E =IR) ='''1.3585V''' Therefore '''Supply Voltage '''required is 5V + 1.3585V = '''6.3585V''' The same power adapter in the link above will probably work OK when the 6V option is selected Hopefully this is of some help.

#### 状态:

open