Help with Halloween circuit

Thread Starter

Somkymon

Joined Oct 1, 2018
2
Hello

I was hoping someone could check over my schematic and offer any suggestions or feedback. I don't know it it will work. I am trying to make a cross rotate upside down to a switch stop and wait a few seconds then return to it's original posotin, hit a switch and stop and wait a few seconds until it rotates upside down again.

Here is my schematic I'm using four AAA batteries:
newest schematic.png

And my PCB

newest pcb.png
Please help
 

AnalogKid

Joined Aug 1, 2013
8,157
The schematic needs work.
All IC symbols should have the same orientation.
Never run races over a component body.
Add decoupling capacitors to all devices.
ALL unused inputs must be connected to something. This is important for all IC's and critical for CMOS devices.
Add reference designators (R1, U3, etc.) to all components. Discussing circuit connections without them is difficult and confusing.
What is the value of VCC?
VCC symbols always point UP.
GND symbols a.l.w.a.y.s point DOWN.

Separate from that ... I won't demand that you fix the schematic before offering advice because I am just such a nice guy.

It looks like the 4001 quad bate is acting as a single inverter. As above, all unused inputs must be tied to either Vcc or GND.

The NOR gate output is tied to the power pin of a 555. This will not work; the gate cannot source enough current. If you want to disable or inhibit a 555, use the Reset input.

Depending on the (secret) motor current, you probably need much fatter GND traces on the board.

Powering one 555 with the output of another 555 is doable, but not at all recommended. The bipolar 555 has a 1.5 V -ish voltage drop between the Vcc input and the pin 3 output in the high state. This means the 2nd 555 is running at a lower voltage, and its high output voltage is that much lower again. Depending on the (secret) Vcc value and the threshold values of the bridge driver, pin 2 might not see a high enough voltage to change state. Again, you're got three unused gates in the 4001; use them to correct logic polarities and drive the 555 Reset pin to force the output low.

ak
 

Dodgydave

Joined Jun 22, 2012
8,477
The timing resistor and capacitor on pins 2,6 , of the 555 are drawn wrong, the resistor should be to pins 6,8. The capacitor to pins 6,1.
 

k7elp60

Joined Nov 4, 2008
555
I agree with what Dodgydave say's about the 555 circuit. I would add that the 480uF may have to much leakage current to allow the capacitor affect the timing. I would suggest a smaller value of capacitor and larger value of R3.
 

Thread Starter

Somkymon

Joined Oct 1, 2018
2
I'm not sure I understand how to place the resistor and capacitor as you decribe. Could you draw what your talking about?
 

Dodgydave

Joined Jun 22, 2012
8,477
I'm not sure I understand how to place the resistor and capacitor as you decribe. Could you draw what your talking about?
The Timing Resistor and Capacitor on pins 2,6 should be like this for an Astable multivib..

tim47.gif

This will give you a pulse high to low on power on, the high to low times are set by the Resistors R1,R2, C1, the low time by R2.
 
Last edited:

Bordodynov

Joined May 20, 2015
2,431
I advise you to use CMOS timers (LMC555), amplify the output of the second timer with two transistors of different structure, to ensure sufficient current supply to the driver.
 
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