Control a car windshield washer pump?

[BigRez]

Hi all -

I've got a 12v windshield washer pump (Trico 11-500 P74) that I want to control with the prop-1.  I cannot find any info on how much power this thing draws but suspect it's probably more than the walwart and/or prop-1 can deliver.  I connected it to the prop-1 (V+ and OUT0) and loaded the simple test program (below.) This works fine with the trainer, but when switching to position2, the prop-1 power LED immediately begins on to blink on and off.  (I also hear the pump make a slight noise with each blink of the light.) Does this mean it's drawing too much power?  If so, what are my options to drive this thing?

Just for kicks (and perhaps showing my electronic ignorance), I tried Jon's High Current add-on device (http://www.efx-tek.com/php/smf/index.php?topic=873.msg4795#msg4795).  Connected to V+, V- and PIN0 and after switching to position 2, got the same effect.

Thanks for any advice.  Test program, last used with the High Current add-on,  follows:


' =========================================================================
'
'   File...... sprayTest1.BS1
'   Purpose...
'   Author....
'   E-mail....
'   Started...
'   Updated...
'   {$STAMP BS1}
'   {$PBASIC 1.0}
'
' =========================================================================


' -----[ Program Description ]---------------------------------------------


' -----[ Revision History ]------------------------------------------------


' -----[ I/O Definitions ]-------------------------------------------------

SYMBOL  Trigger         = PIN6                  ' SETUP = DN
SYMBOL  Sprayer         = PIN0

' -----[ Constants ]-------------------------------------------------------

SYMBOL  IsOn            = 1                     ' for active-high in/out

' -----[ Variables ]-------------------------------------------------------

SYMBOL  timer           = B2
SYMBOL  lottery         = W5                    ' random #

' -----[ Initialization ]--------------------------------------------------

Reset:
  PINS = %00000000                              ' clear all
  DIRS = %00000001                              ' set outputs

' -----[ Program Code ]----------------------------------------------------

  timer = 0

Check_Trigger:
  RANDOM lottery                                ' stir random #
  PAUSE 5                                       ' loop pad
  timer = timer + 5 * Trigger                   ' update timer
  IF timer < 100 THEN Check_Trigger             ' wait for 0.1 sec input

  Sprayer = IsOn

SprayStuff:
  IF Trigger = IsOn THEN SprayStuff

  GOTO Reset


' -----[ Subroutines ]-----------------------------------------------------


' -----[ User Data ]-------------------------------------------------------

[menehune]

A quick web search of replacement washer pumps shows either 2.2 or 4 Amp current draw.  I would design for the 4A current and assume a 5A startup current just to be safe.
The click and flash of the power light means the prop-1 regulator is shutting down due to overload.  I think the onboard regulator is rated to 1A max.  You will probably need to use an external relay with a high current supply (or an automotive battery).

[livinlowe]

I agree, your (probably) pulling too many amps. You'll need a seperate supply.

[JonnyMac]

The reason for the blinking is that the power draw is causing the Prop-1 to reset due to brown-out; after reset the program tries to run again and the cycle repeats.  I'm surprised it did pop the ULN channel.

[ryagl]

I might be way off here but I use a simple battery charger to run my wiper motors with my props.  I have NOT used this with a controller, but  you could use the RC-4 and activate the batter charger instead of the wiper motor directly.  I am not an expert at this, so I would wait for a counter response from Jon.

[BigRez]

I understand that pulling too much power could cause the reset, but don't understand why that would happen until I hit the trigger?  How is power consumed by the pump prior to activating the trigger?

The battery charger and auto battery are good ideas and hadn't thought of those.

Anyone know how I calculate what size wire I need for a 15' run of 12vdc and about 5 amps?

[livinlowe]

Hi all -

...I connected it to the prop-1 (V+ and OUT0) and loaded the simple test program (below.) This works fine with the trainer, but when switching to position2, the prop-1 power LED immediately begins on to blink on and off.  (I also hear the pump make a slight noise with each blink of the light.) Does this mean it's drawing too much power?  If so, what are my options to drive this thing?...

When you switch to position 2, you are applying power to the pump. It probably pulls more than one amp just by powering up. i don't know for sure but if its only happening when you give it power, its pulling too much. I think Jon's right - its amazing you haven't blown the u2803 on channel 0.

[menehune]

I understand that pulling too much power could cause the reset, but don't understand why that would happen until I hit the trigger?  How is power consumed by the pump prior to activating the trigger?

The battery charger and auto battery are good ideas and hadn't thought of those.

Anyone know how I calculate what size wire I need for a 15' run of 12vdc and about 5 amps?

The bigger, the better.  Bigger than you would think.  The current draw will kill you here.  12 Gauge extension cords are relatively cheap, contain two conductors in one jacket and typically available everywhere.  Chop both NEMA plugs off and wire the cord into the circuit.  I don't recommend you use the 120V plug since it's too easy to inadvertently connect 120Vac to the 12vdc load-*Poof*.

http://www.southwire.com/voltagedropcalculator.jsp
Is the 5A a constant current or a peak current?  I will assume 5A constant.
A 15 foot run of 12 gauge copper conductor carrying a 5Amp load will have a 2.17% voltage drop.  You will lose .25V due to the resistance of the wire.  If you are driving a motor or relay, the voltage drop should not be noticable-the motor may run slightly slower than normal.  Sensitive electronics may be affected. 
If you are running the prop at the far end of the 15 foot cable, it should not be affected due to the on-board voltage regulator which steps the 12 volts down to 5V? for the internal electronics.

The I²R losses in conductors is one reason why long distance transmission lines have hundreds of thousands of volts on them-the voltage drop, current flow and conductor heating is reduced, allowing thinner wire to be used.

[EricTheMannn]

I'd recommend a simple 12v relay and separate  power supply for the pump, it will make things allot simpler, you can find really good deals on these guy's online, i got 12 relays for $9.99  on ebay just recently.

-Eric

[JonnyMac]

All Electronics is a great source of low-cost relays.  Hmm... I think I'll pop over there today (I love living in Los Angeles!).

[BigRez]

I too may have to make a visit there next time I drive down to the Valley. (I fly into Hawthorne every other week or so, so stopping is not an option. ;)

I hooked up a 5A power supply today and got better but not correct results.  The pump turned on and started spraying as soon as I flipped the switch to position 2 - the trigger (momentary contact switch) had no impact.  I am using the High Current Add-on that I built but perhaps I've got it connected wrong?  Things seem to work correctly with the trainer connected.

Here's my setup using the same program as in the original post.

Trigger: momentary contact switch at p6.w and p6.r, set up down, no ULN (only because this controller is clipped at p6/p7)

High-current add-on to V+, GND, and p1.w.  And to be sure my electronically-challenged brain understood the schematic for the add-on, the image shows how I will have it wired up. (I've done some reading and noticed that I swapped the base and the collector on the TIP120.)

So, can I get verification that the image below shows the correct connections?

Thanks!

[JonnyMac]

You have the pinout of the TIP120 wrong -- I just used one in a custom design we did for a friend.  Here's the correct pinout:

[BigRez]

Just finished soldering it up (correctly) and saw your post to verify.  (I had also changed my image to show the correct way.)  I've given myself a virtual smack in the back of the head for that one.  :-[

So, I hooked it up and VOILA!  IT WORKS!  Produces a nice flow of water and will work perfectly for my application.

Thanks everyone for the helpful info!