help how do i step up4.5 to 9volts with circuitry no transformers please rc project

Thread Starter


Joined Nov 2, 2010
any help greatly apreciated

converted rc 4.5volt thomas the rail road to leg monorail but motor has tons of torq no speed

the lego motor is meant to have a 9v battery to power it direct

now its got 3 batts in series a positive and negative wire to the first batt +(1.5)-going to the recieverthen next in the series is (1.5)_(1.5)-wire all three leed to the micro cirut board the first red ,oarnge and black
ichecked the voltage and the first two show olny 1.5 volts as they are hoked up to the firts batt for power to the reciever board
the last wire black is 4.5 volst when linked to the first whicch is the pos tive for the reciever

i tried hooking a nine vole ont the last leg and got nothin no functions

al is well ti still works but is torqy and wold like to step up 4.5 to 9 volts

a reciever powered by 1.5 volts and the drive motor 4.5volts
when i increase the voltage to the motor legs of the circut which has for ward and reverse nothing works even thout the 1.5 leg is separte but shares positive to the micro prosessor
any help aprecieated its a suprise lego monorail for x mas now to be rc monorail for my son thnks:cool:


Joined Feb 5, 2010
Stacking several 9volts in parallel wouldn't use up much more room than the AA's. Radio shack carry's 9volt connectors with pre-tinned and stripped wires, ready to solder to. 4 or 5 in a pack should provide enough current to run the motor for several hours. Spending on the front end and going with rechargeable would mean not having to buy constant replacements. You sure you don't have room to squeeze them in somewhere inside the toy? :)

Another choice is spending the 10 to 20 plus shipping for a motor that runs well at 4.5 volts. Turns out, that is about what four 9 volt batteries cost. ;)
Last edited:


Joined Jul 17, 2007
A typical alkaline 9v battery has a ~525mAh rating. NiMH/NiCD 9v batteries are typically 120-150mAh. AA batteries are typically 2200-2500mAh. You certainly get a lot more for your money with the AA batteries.


Joined Feb 19, 2009
Sarge is correct with the batteries.

The only "Decent" 9V I've dealt with are the Lithium which run with 3x3V Lithium inside, they do last a while, but are nowhere near the value for power that AA batteries have reached. The Lithium 9V are still near or over $10!

Thread Starter


Joined Nov 2, 2010
i looked at som video on paralell rc ciruts and teroies that a resistor acros negative and positve terminals will change the sine wave form and draw more current how that will make the motor spin as if it had 9 volts dont know but ill try it
what do you think?

Thread Starter


Joined Nov 2, 2010
Take a look at an ICL7660S.
It would help a lot if you could tell us what the current requirement at 9v is. Most capacitor-switching schemes are really efficient, but pretty low in their output current capabilities.
the little rc device runs on 3aaa batterys in series creatin 4.5 volts the receivers mother board is ran of the first batt in series at1.5 volts but i cant change the voltage going in to 9 because the chip wont oprerat at that level olny 4.7 or lower output to the motor is 4.5 volts in paralell

and switching polarity for forwrd and reverse

i watched the vide on rc paralelle circuts and surmised that the old motor had a campacitorbridge across +& - that must lower the voltage and increase the amps i need to do the oposite do you thik thats right after watching the video on parleel rc ciruts

thnks RobΩ