Hello @crutschow,
I saw your solenoid hit and hold using CD4093 and it looked amazing. I actually have a small application were I need the PWM hit and hold for a 2 Amp solenoid. The solenoid application needs a bit longer delay, so I changed the R and C values to be 22UF instead of 510nf. I have tried the circuit with IRF44z and it worked great. But now I am trying a smaller version with the 4466 mosfet and it simply never goes to the PWM mode. I really do not know what went wrong and I would really appreciate your help. attached are the schematics could you please tell me what went wrong. It is a tiny project but I am really stuck with it.

Many thanks in advance

 

Your schematic is drawn in a way to inhibit understanding of the circuit.

 

it simply never goes to the PWM mode.

With the PWM section disconnected from the MOSFET,
1) Does the PWM section still work as expected?
2) Can the MOSFET be triggered on?

 

attached are the schematics

That's more like a wiring diagram rather than a schematic.
Without seeing the gate symbols for the CD4093 on the diagram, it's too difficult for me to determine what the problem may be.

 

This is the pinout of CD4093.



We don't draw pinouts in circuit diagrams. We use logic gate symbols arranged in a functional left-to-right layout.
Here is an example circuit schematic.

 

I assume that you are referring a circuit diagram similar to this one posted here.

 

That's more like a wiring diagram rather than a schematic.
Without seeing the gate symbols for the CD4093 on the diagram, it's too difficult for me to determine what the problem may be.

Hello Crutschow,
Thank you for your prompt reply.

Basically the circuit I posted is my attempt to turn your hit and hold solenoid circuit, you posted it a while ago (I am attaching it here). Basically the only modification I did was change C3= 22UF to get a longer hit time (12V). When I tested this setup with a simple breadboard it worked just fine. The problem is when I tried to turn it into a small PCB (my experience is limited in that) it did not work. The output is stuck at 12v and never goes to the PWM circuit. I am starting to suspect the CD4093 type used ( CD4093BM/TR ) but I did change it a few times and the same results. When I tried the breadboard version, I used the mosfet 1rfz44n instead of the AO4466 but I dont think the mosfet is the reason. I am really stuck with Why this is happening and would appreciate any input from your side. Thank you very much

 

With the PWM section disconnected from the MOSFET,
1) Does the PWM section still work as expected?
2) Can the MOSFET be triggered on?

Hello,
Thank you for your reply. The PWM section does not seem to kick in and the mosfet is triggered on all time time letting out 12v only. This only happened when I tried to turn the circuit into PCB.

 

hi Fady,
Could you post a good quality photo of your PCB, both sides.?
E

 

I assume that you are referring a circuit diagram similar to this one posted here.

View attachment 291933

Hello MrChips,

Thank you for your reply. Yes the circuit I am trying to make is similar. I did try it on breadboard with a standard CD4093BE and a IRFZ44 mosfet and it worked just fine. It is only when I tried to turn it into a small PCB that the problem happened. The output is always 12v and never goes to the PWM. In the PCB I replaced the CD4093BE with CD4093BM/TR and the mosfet IRFZ44N with AO4466. I really can not tell what went wrong and I would appreciate any help. Thank you

 

hi Fady,
Could you post a good quality photo of your PCB, both sides.?
E

Hello ericgibbs,
Thanks for the reply. Here are the photos. Thank you

 

Hi Fady,
The posted circuit diagram does not match the PCB artwork, so I cannot check the copper tracking, please post the drawing you used for the artwork.
E

 

Hi Fady,
The posted circuit diagram does not match the PCB artwork, so I cannot check the copper tracking, please post the drawing you used for the artwork.
E
View attachment 291964

Hello ericgibbs,
Thank you for your reply. Attached is the circuit I used to make the PCB. I used EASYEDA to make it. I did check the pcb tracks according to the wiring diagram and it all seemed to be fine. I am starting to doubt the CD4093 since the chip they used is CD4093BM/TR and the input to the delay (PIN 1 &2) seems to be always high (12v) even with no components connected to it (I removed the 22uf capacitor). I am attaching clearer photos of the pcb too so it could help. I appreciate your help. many thanks in advance.

 

hi,
The 'B' at the end of the 4093 means the output is buffered, some of the earlier IC's were not buffered, but this should not be a problem for your circuit.

U1 300k should pull pins #1 & 2 to 0V, but the 220uF could cause a problem if say full charged and then H1 header pin#2 was pulled low. This could inject a large negative swing onto pins #1 and 2, which could blow the 4093 input.
I will check and confirm this possibility.
E

 

hi Fray,
The evalue of the cap is just off the image, but it looks like a 22uF.
This simple LTSpice sim shows the negative pulse on the 4093 input when the H1 input goes Low.
E

Edit: what do you consider is the purpose of this section of the circuit.?

 

hi,
The 'B' at the end of the 4093 means the output is buffered, some of the earlier IC's were not buffered, but this should not be a problem for your circuit.

U1 300k should pull pins #1 & 2 to 0V, but the 220uF could cause a problem if say full charged and then H1 header pin#2 was pulled low. This could inject a large negative swing onto pins #1 and 2, which could blow the 4093 input.
I will check and confirm this possibility.
E

hi Fray,
The evalue of the cap is just off the image, but it looks like a 22uF.
This simple LTSpice sim shows the negative pulse on the 4093 input when the H1 input goes Low.
E

Edit: what do you consider is the purpose of this section of the circuit.?

View attachment 291975

Hi,
thank you for the prompt respond. Actually the22uf is the delay function, the whole purpose of the circuit is to start the solenoid with full voltage (12v) for a few seconds and then go to the PWM mode with the voltage selected by the pot.
The 300K U1 should pull pin 1 &2 to 0v after a few seconds (the delays for the solenoid start 12v for a few seconds). weirdly, pin 1 & 2 do not get to 0v. I even tried removing the 22uf and still pin 1 &2 are reading high (12v). Any idea why would pin 1&2 stay with 12v even without C1 being in the PCB?

 

hi,
The input is blown short circuit to +vcc
E

 

hi,
The input is blown short circuit to +vcc
E

Hello ericgibbs,
Thank you for the reply, could you please tell me what is causing the short circuit to the +vcc? I really appreciate your help

 

hi,
When you charge a capacitor to say +12V and then connect the positive side to 0V, the other end of the capacitor becomes -12Volts.
This is could blow and cause an internal short circuit in the 4093, to say the Vcc supply, so most likely the 4093 is damaged.
The circuit you have designed will damage any replacement 4093 you fit, so change the design.
E

 

Hi, @Fady.Soliman
Have you measured the voltage on Pin#1, when the 300k is still connected to 0V and the 22uF disconnected?

Confirm what voltage you measure.
E