A logic gate chip with 1 ea XOR and 2 ea AND gates?

[jellis00]

This picture should be more clear.

Al.

Edit: picture is too small to see details, I attach a zipped one

Anrati, I have designed the Relay Circuit for use with my 16F690 MCU as shown in the attached partial schematic. As you can see, pin RC2 controls one of the two SPDT relays and pin RC3 controls the other. I have purposely wired the ground from the battery rather than the positive terminal to the normally closed contacts on the two relays so that in case there is any leakage in the Solenoid_RED or Solenoid_BLACK wire circuits it won't drain the battery when the relays aren't actuated.

Do you think this circuit will work? One of my concerns is finding a SPDT relay that can be operated within the 25 mA limit of the MCU output pin. Any suggestions where I can get one?

[Archangel]

Hi John,
Why not just use an H Bridge to control your solenoid ?

[aratti]

Do you think this circuit will work?

Yes.

One of my concerns is finding a SPDT relay that can be operated within the 25 mA limit of the MCU output pin. Any suggestions where I can get one

See at this link they have reed relay @ 5V 10 mA.

http://www.americanrelays.com/dip.pdf

Al.

[Charles Linquis]

When I need a strange combination of logic gates that doesn't have to be exceedingly fast, I usually use a small PIC (12F series for example). Small, cheap and can be programmed to any function I need. The best part is that if I want to change something later, I can do it with programming instead of X-acto knives and little blue wires.

[bogdan]

L293d

tle 5205-2

[jellis00]

Yes.



See at this link they have reed relay @ 5V 10 mA.

http://www.americanrelays.com/dip.pdf

Al.

My 16F690 MCU is operating at 3.3 vdc. Therefore I need a relay (SPST or SPDT) whose coil voltage is 3.3 vdc with a coil resistance of 132 ohms or more, and a contact rating for 1 Amp when switching and 0.5 Amps when closed:
3.3 vdc/.025 ma = 132 ohms
Do you know of any sources? I have looked high and low with no success...most have coil resistances that require drive of 50 mA or more which is above 1-pin drive capabilty of the 16F690 and I didn't want to have to use more than one pin to trigger the relay.

I have read that many of the 5V reed relays will still operate at 3.3vdc. What do you know about this?

I appreciate your help. I am going to investigate the suggestion to use an "H-Bridge", but I know nothing about them. Can you point me to any good tutorials on H-Bridges for controlling solenoids that require more current than a PIC will provide?

[bogdan]

what is the model # of your solenoid valve ?

[jellis00]

what is the model # of your solenoid valve ?

bogdan,
Our PIC microcontroller must control a latching valve solenoid, Model L 1/180 1/4"x1/4" as described at http://www.giplindia.com/pdf/water-valve-catalogue.pdf . Here is a description from this document and why we think it is the right choice for use with a microcontroller and battery operation. BTW, why do you ask?
"Brief Design Guide:
􀀹 Life of battery (1.5 V DC X 4 Nos. alkaline) is about 250 000 cycles (only valve
operations).
􀀹 Latching valve operates upto 5 V DC, 60 mS pulse. Hence cicuit should have cut off
voltage or battery low / replace battery indication sutabley.
􀀹 It is prefered to mount latching valve in coil up right position.
􀀹 As supply voltage goes higher pulse width decreases.
􀀹 40 mS pulse is optimum pulse width for valve operation from CLOSE to OPEN
position. For OPEN to CLOSE pisition, pulse width of 20 mS may be kept. This will
maximize battery life.
􀀹 Circuit employed in operation of valve should be of high quality and should have
minimum current consumption in stand by mode to maximise battery life.
􀀹 Test figures mentioned in this document is based on 6 V DC obtained using 1.5 V X 4
Nos. alkaline batteries."

[Archangel]

I appreciate your help. I am going to investigate the suggestion to use an "H-Bridge", but I know nothing about them. Can you point me to any good tutorials on H-Bridges for controlling solenoids that require more current than a PIC will provide?

http://www.mcmanis.com/chuck/robotic...t-circuit.html
http://www.cadvision.com/blanchas/hexfet/np-s.htm
http://www.4qdtec.com/h.html
The simplest 4 transistor h bridge:
http://library.solarbotics.net/circu...arHbridge.html

[jellis00]

http://www.mcmanis.com/chuck/robotic...t-circuit.html
http://www.cadvision.com/blanchas/hexfet/np-s.htm
http://www.4qdtec.com/h.html
The simplest 4 transistor h bridge:
http://library.solarbotics.net/circu...arHbridge.html

Joe: I studied the H-Bridge circuit and I can see now why it is probably the preferred choice for microcontroller use with motor control, and I presume it can be applied in same manner for controller of latching solenoids. Therefore, I have redone our design as shown in the attached schematic, in which we propose to use a ROHM H-Bridge IC model BD6211 or BD6221, depending on what battery voltage we select for solenoid control (see http://www.rohm.com/products/databoo...x_series-e.pdf for data sheet). This IC can be purchased for $1.50 USD at Mouser and greatly reduces the cost and simplifies the circuit layout as compared to using relays. What is your opinion of this schematic?....will it work to control the latching solenoid without fear of "shoot through" during startup of the MCU while it is being initialized and the MCU pin logics are not yet stabilized? At this point that is my only concern about using the H-bridge for latching solenoid control.
Thanks so much for this tip!

[bogdan]

..the clamp diodes are missing...

I think is easy with L293D (internal clamp diodes)...if you combine the channels you have Peak Output Current=1.2A (check the specs of the solenoid)

If you need more current use TLE 5205-2 (peak=6A)

Both of the items should be at mouser.com

...please check also this tutorial to understand better the h-bridge circuit http://www.robotroom.com/HBridge.html