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For the same amount of power (ie Watts), yes, the current would be less as the Volts go up. However, we aren't talking Watts we are talke Volts, Ohms, and Amps.

Try pluging 12 volts and 3.5 Ohms into this Ohm's Law calculator.

http://www.ohmslawcalculator.com/ohms_l ... ulator.php

Then try 24 volts and 3.5 Ohms (the resistors in the hot end are staying the same). You will see that the amps doubles.


(If we wanted to keep the same amount of power output and increase the volts to 24, we could replace the resistors with 28 Ohm resistors (14 Ohm parallel) and then would only push 1.7 Amps.)

edge922 wrote:For the same amount of power (ie Watts), yes, the current would be less as the Volts go up. However, we aren't talking Watts we are talke Volts, Ohms, and Amps.

Try pluging 12 volts and 3.5 Ohms into this Ohm's Law calculator.

http://www.ohmslawcalculator.com/ohms_l ... ulator.php

Then try 24 volts and 3.5 Ohms (the resistors in the hot end are staying the same). You will see that the amps doubles.


(If we wanted to keep the same amount of power output and increase the volts to 24, we could replace the resistors with 28 Ohm resistors (14 Ohm parallel) and then would only push 1.7 Amps.)

Yes, I know ohms law quite well. However, if you are regulating the power using the thermistor to the same typical values, the Average power will be the same, so the Average current will be 1/2 when volts are doubled. It might be appropriate to use larger valued thermistors when going to a higher voltage, then your peak current would lower, too. And yes, the current peaking to double will cause trouble.

I agree in general, though, that it would probably be best to upsize those connectors a bit. Something like these work well:
(a TE Mate-N-Lok), although they only handle 5A. I would still use bigger resistors if your jacking the voltage up

Thanks for the suggestion on the connectors. I'll take a look at the Deans and the Mate N Lock. I ordered some EC2 connectors from Hobbyking and may end up using them. (however they appear to be harder to disconnect than the others).

If I use a Deans , EC2, Or other 2 Position connector for the heaters I will probably use JST for the thermistor.

Also, if I am reading this righ, the RAMBo has a 5amp fuse on the hot end stuff...

edge922 wrote:Thanks for the suggestion on the connectors. I'll take a look at the Deans and the Mate N Lock. I ordered some EC2 connectors from Hobbyking and may end up using them. (however they appear to be harder to disconnect than the others).

If I use a Deans , EC2, Or other 2 Position connector for the heaters I will probably use JST for the thermistor.

Also, if I am reading this righ, the RAMBo has a 5amp fuse on the hot end stuff...

It sounds like you know what you are doing and the fuse is 5 amps although you can replace it with a 10 amp.