troubleshooting a cash drawer solenoid - really... justification for a SCOPE!!!

[rutgrad]

Hello, I am a long time "lurker" in the forums and finally have an opportunity to put some of the knowledge I have gained from the forum and videos to work. I just ordered my DSO1054Z for this project.  Finally have a reason and purpose to acquire my own scope

So here is my challenge...  a point of sale (POS) system uses an Epson receipt printer (TM-T88IV).  The printer has an RJ11 cash drawer trigger port which sends a 24V pulse to activate a solenoid which mechanically opens a cash drawer.  I have tried multiple cash drawers and multiple cables and cash drawer operation is not triggering.  So I figured I would create a breakout cable to test to see whether I am getting any signal, bad signal or incorrect voltage, but I don't want to blow up my new scope when it arrives.  I also I want to make sure my test protocols are correct. 

The RJ11 port is configured as follows:  (I have also included a detailed pdf of the circuit and details of its operation)

Pin1:  Frame GND
Pin2: Drawer Kick-out signal1 (Output)
Pin3 Drawer Closed / open signal (input) "provides drawer state"
Pin4: +24V
Pin5: Drawer Kickout drive signal 2 (Output) "for second cash drawer if required"
Pin6: Signal GND

I presume I should probe pin 4 to make sure it has +24V.  Then probe pin Pin 2 looking for 24V when open signal is sent. 

signal should last according to the following calculation found in teh atacehd PDF (2mS x t1)  where t1 is set to 100mS in our software

I assume i have to set the scope to trigger so the  "capture" occurs.  not sure how to do that but I will certainly try and RTFM when it arrives.  (if I can avoid the urge to probe!)

Sound about right? Any advice would be greatly appreciated. 

[pyroesp]

All (?) scopes come with a little square wave gen of 1kHz. Connect your probe to it and have a play with that (triggering correctly , single shot, continuous, etc) just to have a feel for the scope. Also, there's a tutorial here on how to use a scope, might be interesting to read:
Oscilloscope training class (long)
Also, set your probe to x10 and configure the channel to using a x10 probe (if it's one of those x1 - x10 probes).

I don't see the pdf on your post ?


Down-right, there's the 1kHz sq. wave on the rigol DS1052E.

[CJay]

Nice reason to buy a 'scope but while you're at it, order some capacitors for the TM88 power supply, they go leaky nd cause exactly that problem.

[rutgrad]

Thanks for your replies.  FYI...  I modified my original post to add the missing document.  Apparently it was just a tad too large first time. 

[SL4P]

I think you're working under an incorrect assumption.
The cash drawer does NOT output a 24V pulse.
On page 1 of the PDF manual, it clearly indicates an open collector arrangement, and a 24V supply for the drawer solenoid.

Put the high side side of the solenoid to the 24V rail, and (assuming the solenoid is within the open-collector rating), put the low side of the solenoid on the drawer output pin.

Remember to put a diode across the solenoid to catch EMF kickback.

[PA4TIM]

And then you can use your scope to test the psu for ripple to check if the caps are OK