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

[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

[jellis00]

..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)
]

Granted I forgot the external clamp diodes, but I can't see why you think using the L293D is an advantage over the Rohm BD62x1. Here are compairsons that appear to favor the BD62x1:

Operating range: BD62x1 will run with Vss 3 to 36 v; L293D is 4.5 to 36. This is important to me since my board supply is 3.95 vdc (3 ea AA NiMH batteries);

Quantity 1 price at Mouser: BD62x1 = $1.50; L293D = $5.12....even adding the 4 ea clamp diiodes (1N4001??) BD62x1 approach is a lot cheaper;

Low Stanby current: BD62x1 has standby mode = 10 microAmps; L293D has quiescent current total (Vss + Vx) of at least 18 milliAmps dey pending on logic setting.....this is too high for battery operation.

Based on above comparison I wouldl really appreciate your opinon as to why the L293D is preferable. ???

[jellis00]

Granted I forgot the external clamp diodes, but I can't see why you think using the L293D is an advantage over the Rohm BD62x1. Here are compairsons that appear to favor the BD62x1:

???

Taking a closer look at the Rohm data sheets for their BD622x chips, it appears they also have internal clamp diodes, making it a further advantage for the BD622x1 over the L293D. The chip diagram from data sheet is in the attached image. Am I mis-interpreting this image??

[Archangel]

Sorry for the delay, my ISP is sooooo lame!
Lots of HBridge chips out there, allegro makes a bunch of them, It trumps relays due to cost, reliability, size and they look better too even discrete transistors are still cheaper, smaller, and more reliable, though mosfets might be better than junction types.