Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronic Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Register Log in

Drive 4 triacs with a PIC which is driven by an accelerometer impulse

Status
Not open for further replies.

electricboy

Newbie level 6
Joined
Apr 12, 2011
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,379
Hi I need some help,
I want to transform, in my circuit, a double inverter relay (too big), in an electronic control.
The only way I've found, is 4 triacs (one in each wire the relay was commuting) with their trigger controlled by a microcontroller.
The circuit is driven by a reaction of an accelerometer which inform the chip (with an impulsion) that stops 2 of the triacs and in the same time supplies the others.
The problem is that I need 35mA in each trigger of the triacs and the maximum we should take from the output of a PIC is 5mA and the supply is a battery of 5V.
The second problem is the triacs,are they really reliable if i need a fast answer when i cut the trigger current?
And what is the best PIC to do this circuit (accelerometer and cut/give supply)?
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,670
Helped
14,079
Reputation
28,415
Reaction score
12,742
Trophy points
1,393
Location
Bochum, Germany
Activity points
276,945
Triacs are AC power switches and can't replace relays in general applications. You should clarify the kind of electrical circuit that is involved in the problem.

Particularly triacs:
- can't switch DC currents (they never turn off)
- are only (or mostly) suited for power circuits
- need heatsinks for higher currents and thus are not necessarily smaller than relays respectively contactors
- other than relays don't provide isolation between control and load circuit. Opto triacs (e.g. MOC3030) are often added for this purpose
 
  • Like
Reactions: KJ6EAD

    KJ6EAD

    points: 2
    Helpful Answer Positive Rating

electricboy

Newbie level 6
Joined
Apr 12, 2011
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,379
thanks for the answer,
I know it all but my purpose is a security breaking then my heatsink will be smaller.
i already have my opto but i don't know if i can drive with on impluse of the microcontroller two triacs in the same time. ( the trigger current is 35mA then take 0.7mA from the µC, which go drectly in the opto for isolation and then in an hfe=100 NPN transistor that would give me 70mA, 35 mA for each trigger.)
 

FvM

Super Moderator
Staff member
Joined
Jan 22, 2008
Messages
47,670
Helped
14,079
Reputation
28,415
Reaction score
12,742
Trophy points
1,393
Location
Bochum, Germany
Activity points
276,945
Considering a voltage drop of 1.3V for an IR LED, even a series circuit of both opto triacs inputs can work for 5V supply, saving half of the supply current.
 

electricboy

Newbie level 6
Joined
Apr 12, 2011
Messages
13
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,379
Thank you but do you think i can drive all the triac with one microcontroller because there are just 1 A/D converter in all the PIC I have seen.
I don't even know if i can split the current for both the triacs because after the opto coupler I will be in AC and how could i amplify the current with an AC supply for a DC emitter to the triac's gate?
 

Status
Not open for further replies.
Toggle Sidebar

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top