Can this kit be modified?

[meterman]

I recently purchased this kit. Its an adjustable on/off cyclic timer. www.canakit.com Kit #CK191. I wanted to use it for my fog machine at halloween (15 seconds on and 60 seconds off). My problem is that when adjusting the pots I can only find 2 seconds and 60 seconds. Nothing in between. I was wondering if I can change P1 and P2 to a different value and if so what? and what else would I have to change in order for me to achieve the desired time settings. This timer is made to be adjusted from a few seconds to 30 minutes.

R1, R4, R5 = 1 K Ohm
R2, R3 = 2.2 K Ohm
R6 = 560 Ohm
D1, D2, D3 = 1N4148
P1, P2 = 2.2 M Ohm Trimmer pot
Q1 = 2N4124
C1 = 470 uF/16V
C2 = 1000 uF/10V
C3 = 103/0.01 uF/10n
U1 = NE555
Input is 9VDC or AC

 

[Roff]

Something is wrong with your kit. It should work approximately as advertised. I do have concerns about R4 and R6. If R4 is 0.95*1k, and R6 is 1.05*560, i.e., they are both off by 5%, it may not work. The purpose of R4, R6, and D1 is to force the first cycle to be approximately the same period as all successive ones. If this is not important, these parts can be eliminated. It is highly unlikely they are causing a problem, but you could lift one end of D1 to test it.

 

[Rolf]

I recently purchased this kit. Its an adjustable on/off cyclic timer. www.canakit.com Kit #CK191. I wanted to use it for my fog machine at halloween (15 seconds on and 60 seconds off). My problem is that when adjusting the pots I can only find 2 seconds and 60 seconds. Nothing in between. I was wondering if I can change P1 and P2 to a different value and if so what? and what else would I have to change in order for me to achieve the desired time settings. This timer is made to be adjusted from a few seconds to 30 minutes.

R1, R4, R5 = 1 K Ohm
R2, R3 = 2.2 K Ohm
R6 = 560 Ohm
D1, D2, D3 = 1N4148
P1, P2 = 2.2 M Ohm Trimmer pot
Q1 = 2N4124
C1 = 470 uF/16V
C2 = 1000 uF/10V
C3 = 103/0.01 uF/10n
U1 = NE555
Input is 9VDC or AC

You should find what you need to troubleshoot your circuit here:

**broken link removed**

 

[meterman]

I e-mailed the company and this was their response:

"Please note that CK191 is an economical ANALOG time and therfore it's not meant to be used for short periods of time (such as 60 seconds). I will talk to our marketing people to maybe revise the description to make it clear it's meant for more coarse timing, usually in minute increments and even in that case the timings are only approximate".

The timer is put together correctly and it works. It just is'nt capable of short precise periods like I want. I was hoping that maybe a couple of simple mods could improve it to suit my needs.

 

[Roff]

I e-mailed the company and this was their response:

"Please note that CK191 is an economical ANALOG time and therfore it's not meant to be used for short periods of time (such as 60 seconds). I will talk to our marketing people to maybe revise the description to make it clear it's meant for more coarse timing, usually in minute increments and even in that case the timings are only approximate".

The timer is put together correctly and it works. It just is'nt capable of short precise periods like I want. I was hoping that maybe a couple of simple mods could improve it to suit my needs.

Oh, NOW I get it. All you need to do is change C2 to 47uF. This will make your maximum On and OFF times about 77 seconds, nominally. Component tolerances will cause that to be somewhat different, but you should be able to go to at least 60 seconds, and 15 seconds should be easy to set.

 

[meterman]

Ron H,

I swapped C2 with 47uF as you suggested and it works great. Thanks.

Jeff