David, It is a 10k lin pot fitted to the PCB. Regards Support

Richard, If you run the regulator at 15V you should be fine. 12V may mean that you cannot reach 2000 rpm.

Tony, Plug top power supplies do tend to be the switching type. Linear supplies tend to be much bulkier than their equivalent switch mode types. You can use switch mode but you really need some capacitance across the power supply output. We have not carried out any tests to verify what you would need in terms of capacitance. The RE 280 is only rated to 3V, the RE 280/1 is 12 to 24V so I assume you do mean the RE 280/1. In this case I would suggest a capacitor of 4700uF at 25V.

Paddy, If I remember correctly the Bosch has a full load current of 40A at 24V. If you run it at 12V, you will get about half speed of say 1600rpm. As you have halved the voltage, you have reduced the power by a factor of 4 so your motor is now 187W. Your torque has also reduced by the same factor. The current is likely to have halved as well (assuming you are not over-loading it) so say 20A. This controller is 3A continuous which at 12V is 36W so clearly is not suitable. Firstly, you are wasting this motor by only running at 12V, run it at 24V and gear the output speed down by 2:1. This will also double the torque available which better meets your 'tower' needs. Use a 1506-010 Syren 50 controller which we normally stock but is out of stock at the time of writing. If you are stuck at 12V, then get a 12V motor of the right power and then we can recommend a controller to suit but higher power motors at lower voltages means bigger motor controllers. Best to have a higher voltage motor over a lower voltage motor.

Thanks for your answer. Do you have anything cheaper as I'm only 14 and my parents don't really support me in this stuff I like to do. Thanks

Paddy, Unfortunately we don't. You may well find a cheap scooter controller on EBay but that carries a risk.

I have got two 12v batteries and I am going to link them in series, using wire and lugs. The batteries are

Paddy, You are dealing with power electrics here, whilst not high voltage, it is high current and have their own hazards and demands to consider. You really need to go and do some research on the subject as we are not really here to teach but only to guide. As already mentioned, the motor would like to draw 40A at 24V to delivery its full power. This raises two points with your batteries: 1. SLA batteries are only about 35% capacity efficient at high current draws which in theory means your batteries at full load will only have a capacity of 0.4Ah which means again in theory they will only last 36 seconds before going flat. 2. Batteries have an internal resistance which limits the amount of current they can deliver. Your batteries may have a resistance of at a guess 0.15 ohms and a short circuit current of say 60A. This means that batteries have to be selected not only on how long they deliver current for but also how much current they can deliver. At 40A, two batteries in series means your 24V at the battery terminals will fall to (again in theory to keep it simpler) 12V, the batteries will get hot or worse. We would hate to put you off but you are dealing with delivering 1kW (1000W) of power to the motor if you wish to get full performance from it. This takes careful design and selection of the components used and may not be cheap. We have not even started talking about failure modes and the safety implications. If you wish to proceed, do some research starting with Ohms Law. I was 14 when I started out in electronics (a long time ago!) so can relate to your situation. You may be better off starting with lower powers and work your way up over time. If this is a once off project and no desire to pursue the design side in the future, then find someone else (School Physics teacher?) who can help guide you. We wish you luck and hope you get there.

Paolo, If you are referring to the 950D 1450-102 then yes, it will work as the motor draws less than 1A at nominal load. You did not state the voltage you will be running at as rpm is basically proportional to voltage but at 12V, this motor has a rpm of 1145, 5 rpm would mean a turn down of 230:1 which means a voltage of 0.052V so no, you will not get a rpm of 5. For low rpms, simplu use a motor with a higher ratio gearbox such as the 810:1 version.

Hi, thanks for your explaination. I would actually need a pwm-motor configuration which let me get the motor running from as low as 5rpm to around 1000 rpm (and reverse). This would need to (smoothly) move a small 2kg wheeled dolly (for videocamera movements). Is that possible in any way? I hope you can help me and suggest the best pwm and motor. Thank you. Paolo

Paolo, As explained in my previous post, that is really too much of a turn down of 200:1. At lower voltages and you get significantly lower torques (square law). It may well rotate at those low rpms but you may well find you have to increase the voltage to get the dolly moving and then lower the voltage to get the right speed. As you need smooth operating, pwm controllers have discrete step sizes and depends on the controller. They may have 100 or more steps and whilst these steps will be less noticable at higher speeds, at lower speeds they will be quite evident. Manufacturers do not always specify the number of steps in their pwm controllers including this one. Using closed loop control with a speed feedback can help but the solution we would use is with a stepper motor. However, we have used dc motors for variable speed camera panning with reasonable success with > 100:1 speed turndown but had some fancy custom electronics behind it.

Luke, The most important thing to ensure is that the power supply is not a switchmode type, (MFA refers to this as a digital type). You really must use a linear power supply, I would not get too concerned by half or full wave rectified. You should ensure that the power supply can take the motor starting current as well as well as its full load current.