motors and Prop-1

[dbauer1080]

I would like to incorporate small DC or AC motors, and wiper motors  to turn hanging skulls, and motorize other items in my scenes. If provided amperage and voltage stats, is this a difficult task with the Prop-1/Prop-2? There will be other items being triggered in the scenes(solenoids, AC lights via RC-4 and/or FC-4). Wanted to get an idea of any issues with these motors. Thanks.

[JonnyMac]

Motors can be very tricky and cause all kinds of problems if not dealt with properly.  The best idea is to isolate the motor from the Prop-1 with a relay (two if you want direction control).  About the only motors that you could run safely from the Prop-1 outputs are like those found in toy cars -- limited to 250 mA; and due to the output structure you'd only have on/off control, but not direction control.

[dbauer1080]

I would use small DC motors less than 250mA. Can these go directly from the Prop-1 outputs, or do they require relays? If so, I will soon provide stats on the motors and perhaps ask for help on the relays. For wiper motors, these require up to 5a, so I would assume these have to go through an RC-4, triggering their AC/DC converter power supplies? Looked at Scary-Terry's site and wanted to confirm.

[menehune]

Small DC motors less than 250mA can be connected to the green Outx screw terminals if you have only one running at a time. 

If you want more than one running at a time, the ULN chip cannot handle the current demands and may overheat or go "pop".  If the ULN does die, it is socketed so it can be easily replaced. To run more than one motor at a time you will need a properly rated driver transistor or a relay rated to handle the motor's current.

Switching an external power supply on/off with an RC4 is not necessary.  Depending upon the number of filtering capacitors inside the power supply and the current drawn by the motor, you may have the motor running for a short time after power is turned off if you turn the mains on/off.  It will be better to switch the DC power to the motor on and off since you can control the power with finer control.

[JonnyMac]

I agree with Menehune: use a relay from the Prop-1 to control the DC going into the wiper motor.  If you use two relays you can get on/off and direction control.  If you use the Parallax HB-25 (as Scary Terry has) you can use one pin to get speed and direction control from a wiper motor.

[dbauer1080]

Thanks for your input Menehue and Jon. If I can address the speed issue with voltage via a wall-wart(as Hauntmaster implies), is it still a possibility to turn AC on/off to the wall-wart with an RC-4? Even though it's maybe not necessary, I have 3 RC-4's and plenty of Crydom SS relays. If you feel a relay from the Prop-1 is a better solution, I may need help with the type of relay and the specific way method for connection. The wiper motor is from Monster Guts, is 12VDC with up to 5a draw. The thought of another $49 plus shipping for the HB-25 is daunting if there is a cheaper and practical solution.

As far as the smaller motors, if they all add up to less than 250mA is it still possible to run more than one from a Prop-1, or is the Prop-2 a better alternative for this? This particular scene has some hanging heads that I wanted to have start turning via small DC gearmotors. Thanks again.

[menehune]

Sure, you should be able to turn on a wall wart with the RC4.  It should just look like a light bulb turning on or off.

There are two limits for running motors from the prop1 or prop2.  First is the on board voltage regulator.  The prop 1's on board regulator is only rated to around 1A which is shared between the stamp circuitry and the external loads.  The second (and probably more relevant) limit is the amount of current the ULN chip can provide per load.  I believe the ULN can only deliver 500mA thru one pin, 250ma if only two pins are active.  Here is the thread which lists the specs for the ULN chip.

Since you already have the RC4s and the SS relays, you can test them and see if the performance is satisfactory.  There may be a slight lag between turn off and the motor stopping due power supply filter capacitors discharging.  If the motor positions are critical, you will need to take that delay and/or motor position into account.  If the motors are just spinning a prop (turning a disco ball, rotating a fan blade) with no critical timings, the RC4 solution may be just fine.

[dbauer1080]

Thanks Menehune for the advice.  I'll utilize this info in my scene and reply with any issues.