Gabe Billings
New Member
Howdy. I've got an electronics project I need some assistance with. I think it's pretty basic stuff, but the extent of my electronics knowledge is what I learned in my 9th grade shop class 15 years ago. I've tried to track down answers through on-line electronics guides, but I'm still a little hazy on what I'm doing.
I've got a couple small electric motors; 3v / 290mA and 4.5v 920mA. They were scavenged out of battery powered toys. I got the current readings by putting my multimeter in the circuit while it was energized.
I'd like to make a little project box that I can use to control the speed of both motors as well as power them off of AC current instead of batteries. While doing my research online, it seemed that rather than using a potentiometer for this a better solution was some sort of PWM device. So I tracked down one of those that looked as though it would work. This is what I bought. I put one of the kits together last night and not only did I not burn the house down with my new soldering iron, I managed to get it to work.
My question is how to deal with the incoming voltages into either motor control. I wanted a wall transformer big enough to run both motors and ended up getting **broken link removed** from Digikey. It's rated at 6v 1250mA. Oddly enough, when I checked it with the meter it shows an output of 8.65v. I'm not quite sure what's going on with that.
So I need to know what to do to make sure I don't blow up the motors, especially since the PS I bought seems to be significantly higher voltage than I expected. If I hooked everything up as is it seems as though it would work, but I'd need to be careful not to crank the motor control's pot too far or else I'd overload the motor. Ideally I'd like the correct voltages going into the motor control so I can use the full range to adjust the motor speed.
So this is where I get hazy on what I'm doing. It seems as though I just need a resistor in each circuit to get the voltage where I need it. I don't know if that's the correct answer to this problem and if so if I'm doing my calculations correctly.
3v motor: 8.65v - 3v = 5.65v across the resistor 5.65/.29= 19.5 hm: at 1.6W
4.5v motor 8.65v - 4.5v = 4.15v across the resistor 4.15/.920 = 4.5 hm: at 3.8W
So that's what I've got. I don't know if I'm close or if I have no idea what I'm doing. At least I'm pretty sure I'm not going to electrocute myself. Sorry for the lengthy post. Any assistance would be greatly appreciated.
I've got a couple small electric motors; 3v / 290mA and 4.5v 920mA. They were scavenged out of battery powered toys. I got the current readings by putting my multimeter in the circuit while it was energized.
I'd like to make a little project box that I can use to control the speed of both motors as well as power them off of AC current instead of batteries. While doing my research online, it seemed that rather than using a potentiometer for this a better solution was some sort of PWM device. So I tracked down one of those that looked as though it would work. This is what I bought. I put one of the kits together last night and not only did I not burn the house down with my new soldering iron, I managed to get it to work.
My question is how to deal with the incoming voltages into either motor control. I wanted a wall transformer big enough to run both motors and ended up getting **broken link removed** from Digikey. It's rated at 6v 1250mA. Oddly enough, when I checked it with the meter it shows an output of 8.65v. I'm not quite sure what's going on with that.
So I need to know what to do to make sure I don't blow up the motors, especially since the PS I bought seems to be significantly higher voltage than I expected. If I hooked everything up as is it seems as though it would work, but I'd need to be careful not to crank the motor control's pot too far or else I'd overload the motor. Ideally I'd like the correct voltages going into the motor control so I can use the full range to adjust the motor speed.
So this is where I get hazy on what I'm doing. It seems as though I just need a resistor in each circuit to get the voltage where I need it. I don't know if that's the correct answer to this problem and if so if I'm doing my calculations correctly.
3v motor: 8.65v - 3v = 5.65v across the resistor 5.65/.29= 19.5
4.5v motor 8.65v - 4.5v = 4.15v across the resistor 4.15/.920 = 4.5
So that's what I've got. I don't know if I'm close or if I have no idea what I'm doing. At least I'm pretty sure I'm not going to electrocute myself. Sorry for the lengthy post. Any assistance would be greatly appreciated.