Small DC motor interfering with real time clock?

Hi All,

I'm a bit new to all this, but I'm attempting to build a setup that pumps water with small submersible pumps at a given time. I have everything setup and working. However, when I attempt to power the small DC motor directly from the A0 on my UNO, the RTC starts giving bad date/times.

I am using a 3V/6V DC motor (http://www.ebay.com/itm/like/181889057490?lpid=82&chn=ps&ul_noapp=true). The time library I'm using is by Michael Margolis in the library manager. The RTC is the level shift RTC from Sparkfun.

I set the pin to output. What is odd (or normal) is that I can put the pin high without the pump and everything is fine. As soon as I push the pump into the breadboard, I start getting goofy values.

I'm sure there is some basics I'm missing here but I don't know what it is.

Thanks for any help.

dicemasterflash: Hi All,

I'm a bit new to all this, but I'm attempting to build a setup that pumps water with small submersible pumps at a given time. I have everything setup and working. However, when I attempt to power the small DC motor directly from the A0 on my UNO, the RTC starts giving bad date/times.

Before powering anything from anything, it's important to read the manual/documentation about the power source - such as how much voltage and current (power) can that source supply?

A typical output pin of an arduino can supply up to say 30 mA .... or around that. Apparently the arduino can get damaged if the maximum current output capability is exceeded. Otherwise, if maximum current limits get reached, it may trigger reset circuits in arduino - or other unwanted behaviour.

Instead, the output of the arduino will likely need to be used as a control voltage, which is used as input to a device that is capable of sourcing the amount of power you need, such as a relay device, or a power amplifier device.

Southpark,

That was my suspicion. I will read up on the power requirements and look into relays.

Thanks for getting back to me,

Jeremy

dicemasterflash: However, when I attempt to power the small DC motor directly from the A0 on my UNO

That's a complete no-no, you may have fried the pin permanently - if the overcurrent didn't cook it the over-voltage could have damaged it.

Motors are high current inductive loads, logic signals are low-current and intolerant of high voltage spikes put out by inductive loads.

Thanks MarkT. Lesson learned. I'm running reed relays now and the system is working quite well. Go radio shack.

Thanks again everyone.

J

With a freewheel diode?