Hello, we are an industrial maintenance company in Spain and we are developing a control for the sea gripper with two PWM generators to simulate an opening frequency and a closing frequency at 3,3 volts. We have simulated with the generators a signal of 560hz for opening and 800hz for closing, both at a voltage of 3,3 volts and the result is that it only opens the gripper. To make the gripper open and close , the two simulated frequencies must be simulated at 560hz and at 11,3 volts… Obviously it doesn’t correspond to the factory data…Could it be that the gripper has a defect? Is it possible to drive the gripper with a voltage of order PWM 11,3 volts? Is there any way or device on the market that just controls and powers the gripper? Thanks for helping me with this problem. Kind regards.
Hi @Antoine07, welcome to the forum 
Our Newton Gripper is controlled by a servo-style PWM signal, where the “signal” is determined by varying the pulse-duration, not its frequency. As per the Technical Details:
I’m not sure what you mean by this. The signal sent to the gripper should be 3.3V. Trying to send an 11.3V signal could fry the electronics.
The gripper can be powered with a supply in the 9-18V range, so an 11.3V supply should be fine.
What kind of control (e.g. in operation on an ROV underwater, or for bench-top testing, etc)?
Good morning Eliot and thank you for your quick response.
maybe I’m explaining myself wrong but we use two
PWM generator circuit, one for opening with a 1500us pulse and the other for 1300us closing, both with 3.3v command voltage. With these data the sea gripper does not close, it only opens. We have tried all the possibilities and only by raising the voltage from 3.3V to 11.3v did we get it to close. Could it be an electronics problem? If so, can we have a replacement?We purchased the sea gripper two months ago for bench-top testing but we think there may be a fault in the electronics. Can we use the warranty and send us a new gripper? Our seller is Sea Oupost from Trento (italy) and our correspondent is Andrea.
I thank you for your attention.
Have a nice day
1500µs pulses should get the gripper to stay still. 1300µs should tell it to close (while you’re sending the pulses).
I’m not sure why it would open when sent a stop or close signal unless both sets of your pulses are actually longer than 1530µs (e.g. due to a bad clock in your signal creator, or significant inductance in the signal line, or external electrical noise), or if the gripper electronics are faulty.
A few questions to clarify:
- Are you supplying the signal directly to the signal wire, or do you have some kind of longer wire you’re sending the signal via?
- If you aren’t already, try using a direct connection
- Is your signal voltage relative to the same ground as the power supply?
- If there is no common ground then the signal voltage is floating relative to the power supply, in which case there’s no guarantee it will be detected, and it may cause damage
- Are there other electrical noise sources near your signal line?
- If yes, try to remove them, or at least shield the gripper from them
- Do you have access to an oscilloscope, where you can confirm that the signal voltage is in fact 3.3V, and the pulses are in fact the duration you’re commanding?
- If the signal is definitely correct then that’s good evidence that the product isn’t working as intended, and is good grounds to potentially get sent a replacement
As in the technical details I quoted above, the PWM Logic Voltage should be 3.3V. Too far below that and the gripper won’t register the signal, and going above it may damage the gripper electronics.
I’d recommend going through the questions above.
From there, if you’re quite sure you’re using the device according to its specification but it’s not working as expected then please contact support@bluerobotics.com for discussion of a potential replacement (you can link to this thread to provide extra context).
Given you didn’t purchase it from us it may be that a potential replacement or refund would need to come via your distributor, and given you’ve apparently supplied a signal to the gripper that’s outside the rated voltage it may not be something we can cover, but you’ll get more definitive answers to those points via the support email.
Eliot ,
We have re-checked our test bench together with the sea gripper.
I will answer your questions below:
1. Are you supplying the signal directly to the signal cable or do you have some kind of longer cable that you are sending the signal over?
o If you haven’t already, try using a direct connection.
The connections between the sea gripper and the PWM generators are direct between them.
2. Is your signal voltage relative to the same ground as the power supply? o If there is no common ground then the signal voltage is floating relative to the power supply, in which case it is not it is guaranteed to be detected and may cause damage.
The signal ground is common to the power supply.
3. Are there other sources of electrical noise near your signal line?
o If so, try to remove them, or at least protect the caliper from them.
I can guarantee that there are no sources of noise nearby, the power supply is correct and has a clean signal.
4. Do you have access to an oscilloscope, where you can confirm that the signal voltage is indeed 3.3V and that the pulses are indeed the duration you are commanding?
o If the signal is definitely correct, then it is good evidence that the product is not working as intended, and a good reason to send a replacement.
The signals are verified at 3.3v and the pulses are in the ranges of the specifications.
I recommend reviewing the previous questions.
From there, if you’re completely sure you’re using the device to its specifications but it’s not working as expected, please contact support@bluerobotics.com to discuss a possible replacement (you can link to this thread to provide additional context). .
Since you didn’t buy it from us, a possible replacement or refund may need to come through your dealer, and since you’ve apparently sent a signal to the clamp that it’s out of rated voltage, it may not be something we can. covered, but you’ll get more definitive answers to those points via support email.
I understand your position regarding the guarantee, but the fact that the signal sent later to the ranges of the specifications, is not the fault of the incorrect operation of sea gripper. Please understand that at all times I wanted to be transparent in the information provided about the steps we followed to solve the initial problem.
Based on those responses it does seem like something may be wrong with your gripper. As above, I’d recommend contacting our support email to sort out the next steps from here
I appreciate the transparency on what you’ve tried and the corresponding results - it’s helpful for attempting to diagnose any potential issues, and make suggestions that may help fix them
In a similar vein of transparency, I thought it worth letting you know that intentionally exceeding the electrical specifications of a product to see what happens, before collecting and providing evidence that it wasn’t working properly beforehand, may damage your case for a potential warrantee claim.
That said, I’m not saying it won’t be covered under warrantee, and it’s not my call to make. If we provided you with a faulty product then that’s something we should rectify, but that will be sorted out via the support email - returns, replacements, and refunds aren’t handled via the forums.
By the way, selecting text in a previous comment/post should come up with a “Quote” button that provides the nice quote formatting (and linking).
I can recommend having a look through the How to Use the Blue Robotics Forums post - there’s been a lot of effort put into making it helpful
Eliot,
Thank you once again for your answer.
We have contacted support@bluerobotics.com to explain what happened and we have received an automatic email.
I hope we get a response from tech support as soon as possible.
I’ve learned the lesson, sorry for not using chat well from the beginning.
We stayed in touch.
Have a very good day. 