Good idea on the flashing light, I like that. No, will not ever need any more than three sending locations and three receiving locations. The only receiving station would be behind a counter in the "front", where clients could not see it.

You mean three transmitters (each having three channels) and six receivers, correct? Three transmitters and receivers, one pair in each room, and three additional receivers: back, middle, and reception?

I'm looking at latching remote modules on eBay but they seem a bit pricey to me. I'm thinking we can get away with a less expensive non-latching transmitter/receiver pair and add a toggle flip flop which will turn the momentary signal into a latching one. By using the non-latching type, we can use a 4.5-5.5VDC power supply wall wart and avoid having to add a voltage regulator for the sound module. We can then use LED's that have a flashing circuit built in.

I actually have several of the momentary remote pairs left over from another project, so I'll design a circuit and test it then report back. I may need a few days to do so, but I'll let you know as soon as I have some results. Others may have some better ideas, so I'll continue to keep an eye out.

 

You mean three transmitters (each having three channels) and six receivers, correct? Three transmitters and receivers, one pair in each room, and three additional receivers: back, middle, and reception?

I'm looking at latching remote modules on eBay but they seem a bit pricey to me. I'm thinking we can get away with a less expensive non-latching transmitter/receiver pair and add a toggle flip flop which will turn the momentary signal into a latching one. By using the non-latching type, we can use a 4.5-5.5VDC power supply wall wart and avoid having to add a voltage regulator for the sound module. We can then use LED's that have a flashing circuit built in.

I actually have several of the momentary remote pairs left over from another project, so I'll design a circuit and test it then report back. I may need a few days to do so, but I'll let you know as soon as I have some results. Others may have some better ideas, so I'll continue to keep an eye out.

No, I don't think I need a receiver in the exam rooms...unless it's necessary to indicate whether or not the indicator lights outside the room are on. What I envision is to hit a button to summon help, then hit it again once that help arrives to turn off the indicator light(s).

 

Per inwo's suggestion, I think having a receiver in each room is beneficial so you can "see" that the system is working and also as a reminder to turn it off once help arrives. You can leave off the audio portion to keep disruptions to the other rooms at a minimum.

However, is there ever a condition where a tech is in one of the rooms doing something trivial like cleaning (relative to providing assistance) and you need them to stop and come help?

 

Per inwo's suggestion, I think having a receiver in each room is beneficial so you can "see" that the system is working and also as a reminder to turn it off once help arrives. You can leave off the audio portion to keep disruptions to the other rooms at a minimum.

However, is there ever a condition where a tech is in one of the rooms doing something trivial like cleaning (relative to providing assistance) and you need them to stop and come help?

That would be unlikely.

Yes, I guess it would be beneficial to have an indicator in each room to remember to turn it off.

 

I've thrown together two possibilities. One is using a cheaper momentary transmitter with a latching circuit. Also shown is a master reset to turn everything off with the fourth button if needed. The pro is there is no need for voltage regulators if a 5VDC wall wart such as a cellphone charger is used. The con is the need to build a PCB for all the components.

The other one using a latching transmitter. More expensive, but not by much. This would require a 12VDC wall wart which may add some cost unless you have a few lying around. The sound module requires 5VDC, so I threw in a cheap regulator using a Zener diode. I've shown a edge-trigger for the sound module which may or may not be needed depending on how the sound module operates. If needed, this would be needed in the first circuit too, I just didn't want to make it any harder to read at this point.

I leave this now to others to make suggestions, corrections, or other recommendations . . .

 

PCB?

I'm pre-circuit board ejukated.

 

I'm pre-circuit board ejukated.

Hmm, in that case the second option using the remote system with latching built in would be better - less soldering and work. You'll still need to add a resistor to the LED's and use the Zener circuit, but this can all be put on a small pre-made PCB from somewhere like RadioShack with ease.

I'm looking at these red, yellow, and green LED's from Digikey. They appear to work at 3VDC and blink every 0.4 seconds. Kinda fast, but easy enough to use.

If the soldering isn't a deterrent, I can move forward on the second option with the latching wireless module.

 

The receiver boards have an onboard 78L05. I can load current if it helps.

I'm still not clear on the importance of multiple "calls".

The original 4 button "latch" I suggested, clears with each button press.

 

The receiver boards have an onboard 78L05. I can load current if it helps.

Ah, that may work well to power the sound module and save some soldering. Not sure how much current the sound module requires, but I'm thinking 20-40mA max and only when playing a file.

I'm still not clear on the importance of multiple "calls".

I think the OP wants to be able to let the assistants know which room he or another person needs help in. So three LEDs and three distinct sounds, one for each room where assistance will be needed.

The original 4 button "latch" I suggested, clears with each button press.

I looked at it again and it would work well. I've been looking for less expensive versions only because the OP is going to need six units altogether. I've found some, but the descriptions are terrible so going with the one you originally suggested may be best. I'll continue to look in case I get lucky.

 

I'm not getting the answer I need.
My communication skills may be lacking.

What I mean is, does OP need to be able to call help to a second room without resetting the call to first room.

The 4ch latch, latches on the last button pressed. Resets others. (I think)

78L05 = 100 ma.

Should be fine. 5v drives open collector drivers to 12v relays.

 

@ elec_mech
This really isn't going to be much money. A few hours wages for what an electrician running wire.

It would be in OP's interest to get a spare radio and sound board. Send it to you for evaluation, modification, and pictures.

May not even work the way we think.
Documentation sucks.

 

What I mean is, does OP need to be able to call help to a second room without resetting the call to first room.

Ohhh, I see said the blind man. Hmm, good question. I would assume so in case they have a busy day and multiple rooms need help simultaneously. Probably rare, but I've never worked in a vet's office, so we'll see what the OP says.

The 4ch latch, latches on the last button pressed. Resets others. (I think)

Ah, that would explain why I've had so much trouble understanding the wireless modules I've found. They claim interlock but then explain, rather poorly, that if A is pressed it latches, then B is pressed and it latches while something (unlatching?) occurs to A. If it works as you think (and I suspect you're right), then only one room can "call" for help at a given time. This may not be too bad - the only problem I see is if another room calls for help while the first room to call for help is still waiting.

78L05 = 100 ma.

Yeah, I was figuring on that. As you said, we'd have to measure the current needed by both the receiver and sound module to be sure we remain safely below the 100mA limit.

Should be fine. 5v drives open collector drivers to 12v relays.

Do the relays use 5V or 12V coils? I assume the latter, but if the former, then we could rewire to simply use a 5VDC supply which would be nice.

This really isn't going to be much money. A few hours wages for what an electrician running wire.

A good point. Most of the projects I've helped others with on AAC require a bare minimum of parts and overall cost, so I've assumed the same here. Of course, this requires more labor for circuit assembly which the OP seems to want to avoid. And you are right to mention having a "professional" install something would cost as much or more.

 

Buwah-ha-ha-ha! I think I finally figured out these blasted RF modules.

The most common receiver IC used in these devices is either SC2272 or PT2272. The key to their operation is the suffix. There are three: M4, L4, and T4. The "4" represents four outputs I believe. This listing gave some useful, if poorly, written info. The datasheets for these IC's are even less helpful if you can believe it.

• M4 - momentary; press a button and the corresponding output goes high for as long as the button is pressed; release the button and the output goes low (or floating, not positive here)
• L4 - latching; press a button and the corresponding output goes high; release the button and the same output stays high; press a different button and the first output goes off and the corresponding output goes high; not sure if pressing the same button twice in a row will cause that output (all outputs effectively) to go off or not
• T4 - toggle; press a button and the corresponding output goes high and stays high until same button is pressed again; unlike L4, the outputs, as I understand it, are independent, so you can have two or more outputs high at the same time and controlled independently of one another

Hence, if you look at a close-up of the IC used on the receiver board, we want a T4 suffix. Most are either M4 or L4. I *think* in a pinch one could buy a M4 or L4 wireless module and replace the IC with a T4 which are readily available on eBay. Not ideal of course. Finding pre-built wireless modules with a T4 IC has been challenging, but I located one here and here.

The receiver operates off of 5VDC, so we could power these with the aforementioned 5VDC cellphone chargers as well as the LED's and sound modules without much else. The LED's would still need resistors and we may need an edge-trigger circuit for the sound module (I suspect not, but testing will tell us). Otherwise, I think this may be a winner.

 

What I mean is, does OP need to be able to call help to a second room without resetting the call to first room.

.

Might need to call for help for the second room before resetting call to first room. Probably would be uncommon.

 

Of course, this requires more labor for circuit assembly which the OP seems to want to avoid. And you are right to mention having a "professional" install something would cost as much or more.

Soldering in parts is not a big problem for yours truly. Y

You all have lost me in some of the terminology, but I sincerely thank you for helping me with this project. Like I said...I'm old school electronics: SPDT, DPDTCO...

 

Might need to call for help for the second room before resetting call to first room. Probably would be uncommon.

The only, off the shelf, option is the toggle control.

One button for each room.
Press once for call.
Press same button again for resetting that room only.

That is the reason we suggest having a receiver in each room.
It would be very easy to lose track of which "room call" was on and which was off.

The first link I gave has three call buttons and a master reset. But each "room call" command resets the other "room calls".

Custom logic is possible, but may not be a good idea. Using standard modules is a big plus.

 

I've ordered a couple of the sound modules and a few of the wireless modules to play with. Hope to have them in by the end of the month.

So it sounds like we're looking at three transmitters (one per room) and six receivers with LED's. Two of the receivers will have sound modules for the lab and the pharmacy. The OP has stated no sound for reception and I assume no sound for the rooms, is this correct?

 

That is correct.

 

Got the last item in the mail today. Here is a quick demo I put together showing two remotes operating one receiver with LED's and sound.

So, good news is this is feasible. Bad news is the sound module requires a active low signal and the inexpensive wireless module I selected outputs active high, so I added a ULN2003 IC to invert the signal. This will require a PCB (a generic one can be used) and some soldering. OP, I'm not expecting you to fully understand my description - I mention this in detail in case someone else comes up with a more elegant solution.

The alternative is to use a wireless module with a relay output that has a toggle function. The only ones I came across had a momentary button used to select between momentary, toggle, and the partial toggle inwo first referenced. A little more expensive, but my only real concern is the wireless module somehow defaulting or changing state from the desired toggle mode. You don't want to have to open the enclosure and fiddle with setting the mode if you lose power or the module resets itself for some reason. Perhaps this will never happen, but I don't have one of those and can't say for sure.

 

Way cool.

Yes, you're right, it's over my head. But very cool, that's what I have in mind.